Taking “Xindong 22” as the experimental material，the effect of fertilizer reduction on the changes of photosynthetic physiological characteristics of winter wheat during the filling period was studied.The field experiment was carried out at the Qitai Wheat Test Station of Xinjiang Academy of Agricultural Sciences.Nine fertilization treatments including CF(conventional fertilization)，N4P2，N3P2，N3P1，N2P1，N1P1，N0P1(no N)，N3P0(no P2O5)，and N0P0(no fertilizer) were set up，respectively.The plant height，flag leaf SPAD values，the net photosynthetic rate (Pn)，stomatal conductance (Gs)，transpiration rate (Tr)，intercell CO₂ concentration (Ci)，light energy use efficiency (Eu)，instantaneous water use efficiency (WUE) and yield of spring wheat in the filling stage were studied.The results showed as follows :(1) The plant height and flag leaf SPAD values of winter wheat showed a gentle trend at first and then significantly decreased with the decrease of N and P application rates； There was no significant difference between CF，N4P2，N3P2 and N3P1 treatments.However，with the decrease of N and P application rates，the yield increased first and then leveled off，and the highest yield was obtained when the application rate of N and P2O5 decreased to 240 and 120 kg/hm²， respectively.(2) The Pn，GS，Tr，Ci，Eu and WUE of flag leaves of winter wheat showed a gentle trend at first and then decreased significantly with the decrease of nitrogen and phosphorus application rates.(3) When the application of N and P2O5 was reduced to 240 and 120 kg/hm²，respectively，the plant height，SPAD value，yield and photosynthetic physiological indexes did not significantly decrease at the grain filling stage，and the effect of N application was greater than that of P2O5 treatment.In conclusion，reasonable application of N and P can increase the chlorophyll content of flag leaves of winter wheat at grain filling stage，and promote the growth and yield of winter wheat through photosynthesis，but excessive application of N and P does not promote the growth and yield of winter wheat.Under the condition of N 240 kg/hm² and P2O5 120 kg/hm²，the normal growth and high yield of wheat could be guaranteed.