In order to solve the low utilization and unsuitable ratio of N, P and K in traditional fertilization, soil sample strategy and distribution maps of available nitrogen, phosphorus and potassium were studied. The variable rate fertilization decision support system was developed based on distribution maps. Combined with GPS information, the motor speed of independent fertilizer for N, P and K were controlled to make urea, diammonium phosphate and potassium sulfate be used as needed. The comparative experiment of traditional fertilization and ratio fertilization for corn and soybean in No.5-2 plots of Heilongjiang Hongxing Farm was carried out. Results showed that, with ratio fertilization method, the yield of soybean and corn increased by 2.33% and 9.32% respectively in case of saving fertilizer of 15%.