With the richness of common database resources, distributed users in wide areas hope to transparently access and use these data resources on demand. DS_Grid (database grid) is an SOA (service-oriented architecture) based database grid system for data sharing in multiple application domains. DS_Grid adopts a P2P (peer-to-peer) Multi-Chord (MultiChord) architecture to realize the distributed storage, query processing and dynamic data integration of data resources. According to the text similarity, the data resources are registered to the corresponding domains to realize rapidly discovering data resources. The domain ontology knowledge and reasoning rules are used to support the semantics based intelligent query. A multi-root and multi-peer maintenance based data resources replica management mechanism is applied to improve the reliability of the system. A keyword filter based distributed data integration strategy is adopted to reduce the communication cost. A distributed clustering technique is used to summarize the huge data information. The experiments demonstrate the feasibility and effectiveness of the key techniques of DS_Grid.