The field trials were conducted in south Ningxia province by using regression design of gerneral rotation. By means of establishing mathematical model，the relationship among N,P₂o₅，M and yield was analysised. In addition,a system of optimum model of fertilizing N,P,and M were obtained，with which the output would be above 3 OOOkg/ha in terrace and 2400kg/ha in tableland. Also，the limited line of fertilizer input were given:N 100.5kg/ha,P₂o₅105.0kg/ha,M 30 000kg/ha in terraces and N 110. 0kg/ha,P₂o₅,105. 0kg/ha，M 30 000kg/ha in tableland. Those results could be used in practice to improve yield,save fertilizer and to fore-cast yield.