The characteristics and its tendency of rainfall in Northwest of China play an important role in rain-fed agriculture and soil and water erosion. The paper chose the data of rainfall in Yanwachuan basin from 1981 to 2012 and used concentration ratio, variation coefficient, anomaly, M-K non parametric statistical test and moving t-test technique to analyze the intra annual variation, annual variation and mutation change of rainfall. The result showed that the distribution of monthly precipitation is not even. The concentration ratio is high and precipitation occurred mostly in July and August;the annual variation is small, the average precipitation of long year is 523 mm, variation coefficient of precipitation is about 0.2.M-K mutation test showed that the trend of precipitation change is not obvious and the result is in accordance with that of the analysis of anomaly and variation coefficient.The result of moving t-test technique and M-K test showed that annual precipitation series has no abrupt change point.