Climate change is one of the environmental challenges of the 21st century that is of global concern. The share of industrialized countries in the production of greenhouse gases is higher than other countries. Efforts have been made in some industrialized countries, such as the United States and European countries, to reduce greenhouse gas emissions, but China, the largest producer of greenhouse gases, has not made significant efforts. One of the major changes in global warming is changes in rainfall. In northwestern Iran, the Aras catchment area has experienced a significant shortage of rainfall in recent years. It shows itself to Iran. In order to investigate the precipitation changes of Khoy synoptic station, daily precipitation data and total snowfall for the period 1980-2020 have been received from the Meteorological Organization and after sorting and extracting statistics by Mann-Kendall test have been analyzed. The results of the analyzes show that the monthly precipitation does not have a significant trend according to the Kendall I method. Also, the nature of Khoy precipitation indicates that the first day of precipitation, the number of precipitation days per year, annual precipitation and annual snowfall have a significant decreasing trend. Monthly snow does not have a significant trend. From seasonal precipitation, winter precipitation has a significant decreasing trend. In other seasons, time series do not have a significant trend. In general, it can be concluded that the precipitation characteristics at this station do not follow a specific trend.