Abstract: Using the daily minimum temperature data from 1961 to 2021 provided by Xinjiang Meteorological Information Center and atmospheric circulation index data,based on the conventional meteorological statistical methods,the variation characteristics of the first frost day,the last frost day and the frost period in northern Xinjiang under the different climatic background were analyzed to reveal its changing rule and influencing factors.Results showed that:（1） The first frost date was delayed rapidly with a rate of 0.36 d/a under background Ⅰ,but had small change under background Ⅱ.In contrast,the last frost date was delayed with a rate of 0.15 d/a under background Ⅰ and advance with a rate of 0.28 d/a under background Ⅱ.The frost period was shortened under background Ⅰ and Ⅱ,and the shortening rates are 0.24 d/a and 0.35 d/a,respectively.（2） Under climatic background I,the shortening of frost period is mainly caused by the delay of the first frost date,while under climatic background Ⅱ,the shortening of frost period is mainly caused by the advance of the last frost date.（3） The change trend of the average first frost day in northern Xinjiang is very small under the background Ⅱ because the first frost day is advancing in the west and delaying in the east of northern Xinjiang under this background,and the change trend difference between the delaying and advancing is small;The climate condition background of the average last frost date in the climate background Ⅰ is that the spring air temperature change trend in northern Xinjiang is-0.357 ℃/10 a under this background,and the spatial variation is because the last frost date in northern Xinjiang is delayed as a whole under this background,only the eastern Altay region and the eastern Hami region show an advance trend,and the delay rate is larger,and the advance rate is smaller.（4） From climatic background I to Ⅱ,the grades of the first frost days in northern Xinjiang tended to move from low to high,while the last frost days and frost periods are the opposite.（5） The seasonal North Atlantic oscillation index has a significant effect on the first and last frost days in northern Xinjiang.The first frost days have a significant negative correlation with the summer North Atlantic oscillation index,and the last frost days have a significant positive correlation with the autumn North Atlantic oscillation index.