Based on the hourly precipitation observation of Zhejiang Province and its adjacent area, daily and 3-hourly areal rainfall data of Jinshuitan reservoir basin, ERA5 hourly reanalysis (0.25°×0.25°) and best track data set from Shanghai Typhoon Institute, historical Tropical Cyclones (TCs) that had an influence on Jinshuitan reservoir basin between 2000 and 2016 are investigated statistically. A pair of TCs, Bilis(0010) and Megi(1617) are picked out as they have the most similar tracks while with the most significant rainfall difference. The causes of this difference are investigated in detail subsequently. In spite that Bilis has greater intensity than that of Megi, its areal and maximum accumulative rainfall are both much less than the latter’s. Reasons are as follows. Firstly, Bilis has a faster translation speed and relatively shorter rainfall duration. Secondly, as for the general circulation, the South Asia High (SAH) at 100 hPa is stronger during the lifespan of Bilis than that of Megi, but Bilis is under the control of 16 700 gpm contour, far away from the SAH center, while Megi is within 16 750 gpm area and beneficial for stronger divergence at high level. At middle level, the west Pacific Subtropical High (WPSH) is stronger during the life cycle of Bilis, playing an effective steering role. However, Megi keeps its way between two rings of WPSH, which is not favorable to a fast forward movement. Large-scale water vapor transportation of Bilis at lower level is more vigorous than that of Megi, but Jinshuitan reservoir basin is mainly covered in the water vapor divergent area during the time period we focus, whereas it is in the convergent area during that of Megi, proving to be one of the most important reasons of the marked rainfall difference. Thirdly, multifactorial diagnostic analysis show that Bilis and Megi have similar distribution of specific humidity and vertical component of convective vorticity vector, but when ascending motion and vertical divergence flux are involved, it is found that Megi is much stronger than Bilis. The above result shows that stronger updraft along with stronger lower-level convergence and higher-level divergence is another important reason for the more intense rainfall of Megi.