The data about the growth period of cotton and the daily surface meteorology in Alar reclamation area of Southern Xinjiang from 1990 to 2020 were used to study the dynamic changes in climate resources during the growth period of cotton in Alar reclamation area of Southern Xinjiang under the background of climate warming. The least squares method， Mann-Kendall non parametric test， sliding t-test， and significance analysis were used to analyze the dynamic and sudden changes in climate resources during the growth period of cotton in Alar reclamation area of Southern Xinjiang. The results showed that the precipitation during the whole growth period of cotton in Alar reclamation area of Southern Xinjiang from 1990 to 2020 increased significantly while the relative humidity decreased significantly， with changes of 6.377 mm/10 a and 1.583%/10 a， respectively. The maximum temperature， minimum temperature， average temperature and accumulated temperature did not increase significantly， while the daily temperature range and sunshine duration did not decrease significantly. The main manifestation was that the maximum temperature， average temperature， and accumulated temperature increased extremely significantly while the minimum temperature increased significantly from sowing to seedling of cotton. The daily temperature range increased extremely significantly while the accumulated temperature and precipitation increased significantly from seedling to budding of cotton. The maximum temperature and precipitation increased extremely significantly while the accumulated temperature， daily temperature range， and sunshine duration decreased extremely significantly and the average temperature decreased significantly from budding to flowering period of cotton. The precipitation increased extremely significantly， the daily temperature range decreased extremely significantly， and the relative humidity decreased significantly from flowering to boll opening of cotton. The maximum temperature， precipitation and sunshine duration increased extremely significantly from boll opening to stop growing period of cotton. The changes in various climate factors during other periods of cotton were not significant. From 1990 to 2020， there were sudden changes in the maximum temperature， minimum temperature， average temperature， accumulated temperature， and sunshine duration during the sowing and seedling period of cotton in the Alar reclamation area of Southern Xinjiang in 2014， 1998， 2012， 1997， and 1998， 2005， respectively. The number of sunshine hours during the seedling and budding period of cotton changed suddenly in 2008. The sudden changes in maximum temperature， precipitation， sunshine duration and accumulated temperature from flowering to boll period of cotton appeared in 2001， 2001， 2007， 2003 and 2010. There were no obvious changes from flowering to boll opening period， boll opening to stop growing period and whole growth period of cotton in Alar reclamation area of Southern Xinjiang from 1990 to 2020. It is indicated that cotton farmers should adjust their field management measures in a timely manner based on the values of climate resource and their dynamic changes during the growth period of cotton in the reclamation area.