To achieve the objectives of this study between 80 River station of  Northshore Watershed(covered by Mazandaran province ) were selected, 17 stations in three western, central and eastern of province. According to the statistics, the statistical period 1965-66 to 2010-2011 water year for 44 years were selected as the common statistical period. To evaluate the trend of the most commonly time series, used non-parametric Mann- Kendall test and if there is a trend, for detection of ascendant or descendant trend  used Sen test. According to the results of the three stations in the western part of the province there has been not a clear trend. In the annual sere and winter, autumn seasonal series  of this section as well as some positive trends and rest stations have been no trend that indication of the impact of climate change in particularly cold seasons. In central region of province by study of 6 stations of this area was specified that in the Mahmoodabad-Haraz and Miandasht-Babol stations have ascendant trend of winter and Namarestagh-Namarestagh station have ascendant summer trend and in the Gharantalar-Babol station also have been showed of  winter and autumn seasons  ascendant trend. In the eastern parts of the province only Arabkhayl-Talar stations showed annual and summer rainfall trend and the rest of the stations investigated were no clear trend.