According to the 4 years(2009-2014)daily rainfall data of mainland china from the China Meteorological Data Service Center(CMDC), the precision of TRMM precipitation data is evaluated by indicators such as error, correlation coefficient, and relative error on the time scale of months and years respectively. The results show the TRMM precipitation data is of high accuracy on the monthly and annual scales. The monthly correlation coefficient is 0.99 and the annual correlation coefficient reaches to 0.86. The accuracy of TRMM precipitation data is mainly affected by precipitation intensity and altitudes. In arid and high-altitude regions the accuracy of the TRMM precipitation data is low.