Abstract: Satellite-based precipitation product plays a significant role in analyzing spatial pattern of precipitation. TRMM 3B42 (3B42), as one of important precipitation products, is a key forcing factor for ecological, climate and hydrological models with its sufficient spatial and temporal scales. At present, there is still limited knowledge of accuracy and error structure of new version 3B42 V7, especially the lack of evaluating its accuracy in regions of mid-high latitudes, which restricts its application in the field of ecology, climate and hydrology. Based on 3B42 V7 product and data obtained from 53 weather stations in the period of 1998-2012 over Inner Mongolia, the paper evaluated the accuracy of 3B42 and revealed the spatial distribution of accuracy evaluation indices and its influencing factors. The result of overall accuracy evaluation indicated that there was overestimation of the amount of precipitation by 3B42 at daily, monthly and annual timescales. Error of 3B42 increased with the increasing  timescale, and mean error and mean absolute error of daily precipitation were just -0.06 and 0.88 mm, respectively. It showed good performance for detecting the occurrence of rain events with equitable threat score (ETS) of 0.23, but slightly overestimated the frequency of rainy events. Moreover, altitude and average annual precipitation had impacts on data accuracy. The absolute error of precipitation decreased and yet the ability of detecting rain events became weak with the increasing  altitude, while the effect of average annual precipitation on data accuracy was opposite.