The “3414” experiment was designed to study N,P,K fertilizer combined application effects on Allium cepa L.yield and the optimum fertilizer recommendation rates when reached the maximum yield and the optimum economic yield in Anqiu area.The results showed that the application of N,P,K fertilizer could significantly increase the yield of Allium cepa L.,with a largest increase rate of 103.99%.The combined application of N,P,K fertilizer had significant interactions with each other and increased the yields with the order of K > N > P,while yield of the treatments of high fertilizer application levels showed a decreasing trend.Based on the fertilizing model,the fertilizer quadratic model was not suitable for this test.Through the appropriate fertilizer models based on the yields,it could be concluded that for the Allium cepa L.the maximum yield could be reached when N，P2O5，K2O were applied with 1 443.4，2 359.4，1 632.0 kg/hm2 respectively,and the optimum economic yield could be achieved with 1 343.2，1 852.3，1 400.2 kg/hm2 respectively.