Groundwater simulation has become an essential procedure on the groundwater resources management and assessment. There are many stand-alone pre-and post-processing software packages to alleviate the model simulation loading, but the stand-alone software do not consider centralized management of data and simulation results neither do they provide network sharing functions. Hence, it is difficult to share and reuse the data and knowledge (simulation cases) systematically within or across organizations. Therefore, this study develops a centralized and network based groundwater modeling support system to assist model development. The system is based on service-oriented architecture and allows remote user to develop their modeling cases on internet. The data and cases (knowledge) are thus easy to manage centralized. MODFLOW is the modeling engine of the system, which is the most popular groundwater model in the world. The system provides a data warehouse to store groundwater observations data, MODFLOW Support Service, MODFLOW Input File & Shapefile Convert Service, Model Simulation and Parameters Identification By Expert System to assist model building. Since the system architecture is service-oriented, it is scalable and flexible. The system can be easily extended to include the scenarios analysis and knowledge management to facilitate the reuse of groundwater modeling knowledge.