The exploitation and utilization of saline-alkali land is an important way to supplement cultivated land and ensure national food security. Strengthening the dynamic monitoring and mastering the movement law of water and salt are the bases of taking measures timely to improve the utilization of saline-alkali land. Based on the WebGIS platform and Microsoft Silverlight technology, a dynamic monitoring system was designed and developed for salt and water in saline-alkali land. The system realized the functions such as field parcel information query, statistical analysis, spatial analysis, dynamic trend analysis and early warning, and the system was applied in the saline-alkali land in Wudi County of Shandong Province. The results showed that the system can assist users to grasp the dynamic information of water and salt in saline-alkali land timely and comprehensively, thus can provide decision support for field management.