A heavy rainstorm on 17 August 2007 in Shandong Province was studied on the mesoscale characters by the data of conventional and AWS observations, satellite, Doppler radar, lightning location instrument and WRF simulation. And the sensitivity experiment of numerical model was carried out to investigate the influence of topography. The results are as follows. The heavy rainstorm was caused by the K H instability, wind shear and vortex. Meanwhile, terrain played an important role in the location and intensity of rainstorm, which brought more rainfall and made heavy rain located in the further south area. The numerical simulation comparison test was worked between the two similar rain processes. The result shows that there are more obviously consistences in many ways, including rainfall area, central intensity and distributions except the intensity of heavy rainfall. The terrain has a stronger effect to the heavy rainfall. The wind shear caused by terrain made stronger vapor convergence and vertical velocity. What’s more, the terrain also affected the distribution of cloud vapor and rain vapor. As a result, the favorable circulation and terrain are the important factors to produce the heavy rainstorm.