The function model of rice yield under the different N, P, K applying amount and density in field was established by the orthogonally block twice regression rotation combination design.The result showed that: the order of the factors affecting rice yield was N applying amount＞P applying amount＞K applying amount＞density.N,P or N,K are replaceable to some extent on the equal yield line.The analysis using the principle of border effect showed that a tiptop yield of 9 079.8 kg/hm² could be reached when N,P,K applying amount were 189.4 kg/hm²,108 kg/hm²,144.1 kg/hm² respectively and the planting density was 16.2 hole/m².