A Fertilizer Decision Support System was developed based on the long term maize field experiments in Shuangcheng County located in black soil region, Northeast China. In the study, 500 soil samples in the0-20cm layer were collected from the cor nfield in all the Shuangcheng County and the support scheme of the system was established by the long-term experiment in the field and fertilization model. The geostatistics and Kriging methods were used in the study in order to analyze the spatial heterogeneity of soil nutrients and make the map of fertilization management unit. The Java Script Language was used to develop the Fertilizer Decision Support System on ArcGIS Servers. Using this system, agronomists and decision makers can obtain information on the spatial variability of soil fertility and make decision on strategic management on soil fertil-ity. In addition, far mers can access the system to obtain their fertilizer recommendations easily. This research provides a useful tool to promote the application of agricultural information through WebGIS, to increase farmer's profit, and to improve sustainable agriculture and environment protection.