To achieve the goal of grid computing, scalable and effective mechanisms for representing, managing, and retrieving diversiform grid information are required. This paper presents an XML-based Grid Information Management System (XGIMS), which implements grid information modelling and retrieval. With GLUE specification, an extensible schema service is proposed, which supports user-defined resource schemas. Different from lots of existing approaches, an index- based XML parser is used to build indexes of grid resources based on the model. Furthermore an index- based XPath engine is presented for efficient and flexible query. XGIMS has been applied to the Information Service in ChinaGrid and the experiment results proved its efficiency.