Abstract: To study the impact of different levels of urea or diammoninm phosphate on watermelons yield and its fertilizer utilization rate. The results showed it improved the yield of watermelons by different levels of urea. Combined application of urea and diammonium phosphate fertilizer also improved the yield of watermelons. Within the range of 150-300kg urea per hectare, application 300kg/hm2 urea significantly improved yield. When 150kg/hm2 urea applied, there was the highest yield of watermelons with 450kg/hm2 diammonium phosphate applied;the benefit equation of using mixed Carbamide and Diammonium phosphate as fertilizer in high and middle yield field was Y=46405＋53.918x-0.0667x2 and Y=30618＋21.943x＋0.0118x2. The nitrogen fertilizer utilization rate was 18.4% and 28.6% by Single application of urea 150kg/hm2 and 300kg/hm2, respectively. The diammonium phosphate fertilizer utilization rate was 19.6%-29.0% in the range of 150-450kg per hectare. High yield field fertilizer utilization rate was 10.2% in the range of 600kg per hectare.