Selecting precipitation data of Yushu County from 1953 to 2013, based on standardized precipitation index (SPI), the drought and flood intensity, frequency distribution and periodic characteristics of Yushu County were studied by using the frequency analysis, wavelet cycle analysis and other methods. The results show that (1) there are different drought and flood indicator degrees between the three scales of standardized precipitation indexes (SPI-3, SPI-6 and SPI-12); (2) In recent 61 years, the occurrence probability of severe droughts is 2.1%, the occurrence probability of severe floods is 1.3%; (3) In Yushu County, the flood frequency will increase in next few years; (4) The precipitation changes with a primary period of 18a in Yushu County.