A toolkit called DartGrid 1 using technologies from either semantic web or grid is introduced. It is build upon Globus Toolkit and uses RDF-based ontology to integrate heterogeneous relational databases. Technically, database resources are exposed as grid services and organized as an ontology-based virtual organization. By uniformly defined domain semantics, data resources are semantically registered to an semantic registration service and seamlessly integrated together to provide unified semantic query and semantic search service. Furthermore, a set of semantic tools are developed to raise the level of interaction with the system to a semantic level. A visual mapping tool is offered to help data provider to define semantic mapping from relational schema to shared ontology. A visual query tool which can automatically generated query interface based on ontology definitions, is provided to help specify complex semantic queries. A search-engine-like interface is offered to enable quickly search and semantically navigate data from one database to another database. DartGrid is a deployed system that currently provides query and search service at China Academy of Traditional Chinese Medicine.