The invention discloses a downscaling correction method of precipitation data of a mountain satellite. The method comprises the following steps: reading of TRMM 3B42.V7 satellite precipitation data and carrying out monthly precipitation statistics; carrying out correcting variable fusion and spatial scale unification; establishing a regression downscaling model; and carrying out cross validation and downscaling correction execution. According to the invention, the observation precipitation data of the mountain meteorological station are fused into the downscaling correction process of the satellite precipitation data and the method optimization is carried out by using the cross-validation technology, so that advantages of the limited observation data in the mountain area are fully utilized, the precision of the precipitation after the down-scaling correction and consistency with the measured data series are greatly improved. In addition, the invention also puts forward a multi-method comparison reviewing type downscaling correction technique, so that a system deviation problem of the single downscaling correction method is solved, the satellite precipitation data downscaling correction method system is enriched, and the credibility of the results is enhanced. According to the method, the adaptability to the downscaling correction of typical mountain satellite precipitation products is enhanced; and related results can provide strong support for the system to grasp the temporal and spatial distribution characteristics of precipitation in mountainous areas.