To realize the nitrogen(N)nutrition diagnosis for drip-irrigated winter wheat in Ta′e basin and determine the appropriate nitrogen application rate，field experiments during 2020—2021 were conducted. In this study，the variety of ‘Xindong 18’ was selected，and five N application rates(0，80，160，240 and 320 kg/hm²)were set up. The effect of different N application rates on wheat aboveground biomass and plant N concentration were analyzed，and a critical N concentration model was developed. After then，the N nutrition index(NNI)of winter wheat under different N application rates were calculated，its relationship with relative yield was analyzed，and ultimately the N nutrition status of plant was determined. The results showed that at each growth stage of winter wheat，the difference of plant biomass and N concentration were significant when N application increased from 0 to 240 kg/hm²，while it was not significant when N application increased from 240 to 320 kg/hm². The fitted curve between N application rate and yield showed that after a certain amount of N application，increasing N application would reduce the yield of winter wheat，indicating that there was a phenomenon of N extravagance consumption. The critical N concentration model of winter wheat based on aboveground biomass and N concentration was Nc=3.088DM-0.374，the determination coefficient R2 of the model was 0.918，and the test parameter n-RMSE was 8.89%，which indicted the high stability of the model. The NNI calculated based on the critical N concentration of plant indicated that the suitable N application rate for winter wheat was 160-240 kg/hm². The correlationship between NNI and relative yield in each growth stage was significant. In conclusion，the developed critical N concentration model and NNI of winter wheat in Ta′e basin could better diagnose and evaluate the N nutrition of winter wheat.