Abstract: In this study, a field experiment was conducted in a randomized block design with triplicates. Chuanxiang-you 9838 was used to investigate the variations of yield and panicle-grain structure of mid-season hybrid rice at different ecological site under application of nitrogen application (ANA) and ratio of postponing nitrogen application (RPNA) in 2011 and 2012. Data showed that ANA treatment and RPNA treatment has different effects on grain yield at different ecological site. Tested sites have highly interaction effects with ANA and RPNA, respectively, and the increase effects of RPNA in yield as well as optimizing application amount of nitrogen have a remarkable negative correlation with soil basic fertility. When the rice yield from paddy soil fertility was over 7000 kg/ha, no increase effect of RPNA in yield was observed. The effects on increase in yield for the RPNA treatment mainly was exhibited by little amounts of ANA with lower ratio of RPNA, and the increase in grain yield were maintained by effective panicles duo to increases in effective panicle number and the weight of 1000-grain. This study proposed a positive and highly efficient management approach in nitrogen application for mid-season hybrid rice in Southwest China.