Abstract: Based on the data of winter average temperature (T_m) at Nyingchi station in Xizang from 1991 to 2022, the data of winter wheat growth period and atmospheric circulation index, according to the warm winter grade (GB/T 21983-2008). the variation characteristics of warm winter index (IWs) in Nyingchi in the past 32 years and its influence on the winter wheat growth period and its causes were analyzed by linear tendency estimation, correlation coefficient analysis and Mann-Kendall. The results showed that: (1) In winter, T_m increased significantly at a rate of 0.40 ℃/10a in Nyingchi, and the mutation occurred at the beginning of the 21st century. Among them, the mutation time of T_m in January was the earliest (1999), but the warming rate was the smallest (0.30 ℃/10a), the mutation time of T_m in December was the latest (2009), and the warming rate was the highest (0.47 ℃/10a). (2) The IWs increased significantly in Nyingchi, and there were 10 warm winter events, including 3 strong warm winters and the most in 2000s during the period. (3) The significant increase of IWs led to the advanced regreening stage and setting stage of winter wheat, and the overwintering period shortened significantly by a rate of −2.63 d/10a. (4) In winter, the A and B indexes of the Tibetan Plateau were larger, the sunspot index was lower, the area index and intensity index of the western Pacific warm pool were stronger, and the monsoon index was weaker, which was prone to warm winter in Nyingchi.