Snow cover is one of the major sources of water in most part of the world and also in mountainous areas. The large part of rainfall in Iran?s mountainous basins i in the form of snow, thus water from snow melting has important role in the formation of surface runoff and ground water recharge. Snow cover is indicator of the amount of stored water in highland basins and it is an important factor for predicting basin?s stream by hydrological models, thus the spatial and temporal monitoring of snowy cover is of highly importance. Lack of sites, and meteorological data and suitable snow survey in the basin increase importance of using remote sensing to determine level of snowy surface. The most efficient methods of continuous monitoring of snow cover is based on remote sensing or satellite images. The aim of this study was to investigate possible changes in snow cover area due to survay of changing in rainfall and temperature in the DEZ basin and its impact on water resources. In this study, the level of snow cover was processed with Terra and Modis satellite images in Envi software setting and then with respect to the program which wrote in Matlab software, basin?s snow was extracted cover for statiscal period 2001-2014 with time intervals of seven days (728 snow cover map). Analysis was carried on images of days with least clouds or no clouds. From meteorological stations calculated temperature average and total rainfall in basin. At last, due to program which written in Excel software by using Mann-Kendall nonparametric the Trend Free Pre-Whitening Statistical mean of snowy surface and mean sum of temperature and total precipitation of the basin was trending for the statisitical period. The Z score of snow cover trending was -0.427 that this amount is not at the level of 1% as well as significant at the 5% level. Like wise, slope of trend line is equal to -3.74. Z is result rainfall trending equal to -1.65, that due to possibility shows that rainfall decreased and this decrease is significant at 1% and 5% level. The results of temperature trending were progressive, but with respect to the amount of Z = 0.43, it is significant. Finally, due to trending results, one can conclude that reduction of snow surface at statistical period was because of rainfall reduction in basin and increasing of temprature that decrease snow level, but in this assessment it was not effective parameter for that special years. Keywords: Snow cover, MODIS, NDSI, MK-TFPW test, DEZ Basin