Climate change in the arid area of Xinjiang is obvious in recent years.Whether there is a threshold value for grassland ecosystem response to atmospheric nitrogen deposition and climate change in this area needs to be further studied.This paper takes the four types of grassland (alpine meadow (AM),mid-mountain forest-meadow (MMFM),low-mountain dry grassland (LMDG) and plain desert grassland (PDG)) in the northern slopes of Tianshan Mountain as research object,based on the DNDC model,to reveal the influence of atmospheric nitrogen deposition and climate change on the grassland net primary productivity (NPP).The results showed that:1) there was a threshold value of NPP response to nitrogen deposition,and the response thresholds of PDG,LMDG,MMFM,and AM were 20±5.77,60±26.46,50±15.28,and 30±11.55 kg·hm^-2,respectively;2) the hydrothermal condition was the main factor determining NPP;3) there was a threshold value of NPP response to temperature rise in PDG grassland,while no definite conclusion had been drawn for the other types in the current study;4) the NPP of PDG and LMDG grassland was positively correlated with precipitation,while the change of AM grassland NPP was negatively correlated with precipitation.The sensitivity of different grassland types to precipitation changes also varied greatly,with PDG being the largest,followed by LMDG,AM,and MMFM.