Abstract: In order to understand photosynthetic characteristics of korla fragrant pear and its response to soil nutrients N,P,K at fruit setting stage,the diurnal variation curves of photosynthetic characteristics of korla fragrant pear under different treatments of N,P,K were measured by portable photosynthesis system CIRAS-2 in the field conditions. The results showed that the diurnal variation curves of Pn of Korla Fragrant Pear presented double-apex curves,and had a phenomenon of photosynthetic "noon breaking". It can promote the net photosynthetic rate of leaves to apply fertilizer N,P and K,but over-fertilizers brought no benefit. Through the establishment and analysis of model,the role of fertilizer N,P and K to Pn of Korla Fragrant Pear leaves was in order:K >P >N. The interaction effect of P and N,K and N were positive,but K and P were antagonistic.Taking the Pn as optimal composite scheme,the rate of N was 200 kg·hm^-2~250 kg·hm^-2,the rate of P 300 kg·hm^-2~350 kg·hm^-2,while the rate of K 50 kg·hm^-2~55 kg·hm^-2.