In this study, by using the Mann-Kendall nonparametric method and Sen' s Estimator slope test, the trend of some elements including  precipitation, average of maximum and minimum temperature and the  number of snowy days Chaharmahal and Bakhtiari Province covers part of Zagros and Zardkohe-Bakhtiari highlands, from which three major rivers including Zayandehrud, Dez and Karun originate. in an annual and monthly scale, was evaluated in  the stations of the province during a period of 30 years (1986-2015). The output was presented in the form of tables, graphs and iso-trend maps as drawn in the Arc_GIS. The results showed that although changes in rainfall did not follow any specific trend in most months of the year, the amount of precipitation in the stations of Koohrang as the rainiest station in the Province, Lordegan and Yan-Cheshme had a decreasing trend at the significance level of 99%; also, the the number of snowy days during March showed a decreasing trend in Koohrang station. However, the average minimum and maximum temperature in most areas of the province, in both monthly and yearly scales, except for the months of November and December, had a significantly increasing trend.