diff --git a/memos/config.py b/memos/config.py
new file mode 100644
index 0000000..3b9c04a
--- /dev/null
+++ b/memos/config.py
@@ -0,0 +1,11 @@
+import os
+
+# Define the default database path
+DEFAULT_DB_PATH = os.path.expanduser("~/.memos/database.db")
+
+# Function to get the database path from environment variable or default
+def get_database_path():
+    return os.getenv("MEMOS_DATABASE_PATH", DEFAULT_DB_PATH)
+
+# Ensure the directory exists
+os.makedirs(os.path.dirname(DEFAULT_DB_PATH), exist_ok=True)
\ No newline at end of file
diff --git a/memos/models.py b/memos/models.py
new file mode 100644
index 0000000..563287f
--- /dev/null
+++ b/memos/models.py
@@ -0,0 +1,112 @@
+from sqlalchemy import (
+    create_engine,
+    Integer,
+    String,
+    Text,
+    DateTime,
+    Enum
+)
+from datetime import datetime
+from sqlalchemy.orm import relationship, DeclarativeBase, Mapped, mapped_column
+from enum import Enum as PyEnum
+from typing import List
+from .config import get_database_path
+
+
+class MetadataSource(PyEnum):
+    USER_GENERATED = "user_generated"
+    SYSTEM_GENERATED = "system_generated"
+    PLUGIN_GENERATED = "plugin_generated"
+
+
+class MetadataType(PyEnum):
+    EXTRACONTENT = "extra_content"
+    ATTRIBUTE = "attribute"
+
+
+class Base(DeclarativeBase):
+    pass
+
+
+class Library(Base):
+    __tablename__ = "libraries"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    name: Mapped[str] = mapped_column(String, nullable=False)
+    folders: Mapped[List["Folder"]] = relationship("Folder", back_populates="library")
+    plugins: Mapped[List["Plugin"]] = relationship("LibraryPlugin", back_populates="library")
+
+
+class Folder(Base):
+    __tablename__ = "folders"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    path: Mapped[str] = mapped_column(String, nullable=False)
+    library_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    library: Mapped["Library"] = relationship("Library", back_populates="folders")
+    entities: Mapped[List["Entity"]] = relationship("Entity", back_populates="folder")
+
+
+class Entity(Base):
+    __tablename__ = "entities"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    path: Mapped[str] = mapped_column(String, nullable=False)
+    filename: Mapped[str] = mapped_column(String, nullable=False)
+    size: Mapped[int] = mapped_column(Integer, nullable=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False)
+    last_modified_at: Mapped[datetime] = mapped_column(DateTime, nullable=False)
+    filetype: Mapped[str] = mapped_column(String, nullable=False)
+    last_scan_at: Mapped[datetime | None] = mapped_column(DateTime, nullable=True)
+    folder_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    folder: Mapped["Folder"] = relationship("Folder", back_populates="entities")
+    metadata_entries: Mapped[List["EntityMetadata"]] = relationship("EntityMetadata", back_populates="entity")
+
+
+class Tag(Base):
+    __tablename__ = "tags"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    name: Mapped[str] = mapped_column(String, nullable=False)
+    description: Mapped[str | None] = mapped_column(Text, nullable=True)
+    color: Mapped[str | None] = mapped_column(String, nullable=True)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False)
+
+
+class EntityTag(Base):
+    __tablename__ = "entity_tags"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    entity_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    tag_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    source: Mapped[MetadataSource] = mapped_column(Enum(MetadataSource), nullable=False)
+    created_at: Mapped[datetime] = mapped_column(DateTime, nullable=False)
+
+
+class EntityMetadata(Base):
+    __tablename__ = "metadata_entries"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    entity_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    key: Mapped[str] = mapped_column(String, nullable=False)
+    value: Mapped[str] = mapped_column(Text, nullable=False)
+    source: Mapped[MetadataSource] = mapped_column(Enum(MetadataSource), nullable=False)
+    datetype: Mapped[MetadataType] = mapped_column(Enum(MetadataType), nullable=False)
+    entity = relationship("Entity", back_populates="metadata_entries")
+
+
+class Plugin(Base):
+    __tablename__ = "plugins"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    name: Mapped[str] = mapped_column(String, nullable=False)
+    description: Mapped[str | None] = mapped_column(Text, nullable=True)
+    webhook_url: Mapped[str] = mapped_column(String, nullable=False)
+    libraries = relationship("LibraryPlugin", back_populates="plugin")
+
+
+class LibraryPlugin(Base):
+    __tablename__ = "library_plugins"
+    id: Mapped[int] = mapped_column(Integer, primary_key=True, index=True)
+    library_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    plugin_id: Mapped[int] = mapped_column(Integer, nullable=False)
+    library = relationship("Library", back_populates="plugins")
+    plugin = relationship("Plugin", back_populates="libraries")
+
+
+# Create the database engine with the path from config
+engine = create_engine(f"sqlite:///{get_database_path()}", echo=True)
+Base.metadata.create_all(engine)