Abstract: A numerical simulation has been performed with the mesoscale non-hydrostatic model WRF (Weather Research Forecast) to study the torrential rain associated with Typhoon Bolaven(2012) in Northeast China, and the detailed comparison between the simulated results and the observations has been conducted. Furthermore, by using the high resolution model outputs, a diagnostic analysis has been also carried out to gain a better understanding of the torrential rain and precipitation asymmetric distribution mechanism. The results indicate that the simulated track, intensity and rainfall of Typhoon Bolaven all match with the observations well. After landfall of Bolaven, its precipitation distribution and its circulation showed clear asymmetric structure because of the intrusion of the north cold-dry current from the middle latitude trough into the typhoon circulation. The rainfall mainly occurred near the energy front zone located in the northwest of the typhoon. The moisture divergence flux and moisture vertical helicity can well describe the genesis and spatial-temporal variation of the torrential rain and its asymmetric distribution of Bolaven. The moisture divergence flux shows strong signals in positive value and the moisture vertical helicity shows strong signals in negative value over the torrential rain areas. And they display weak signals over the non-rainfall or weak rainfall areas. Convective instability provided a favorable condition for the precipitation only in the initial stage of the typhoon rainfall, and the moisture baroclinic item MPV2 of MPV was the major mechanism for the torrential rain enhancement and its asymmetric distribution. During the process of torrential rain formation, the vorticity over the precipitation area was increased greatly by the isentropic surface slantwise and the vertical shear of horizontal wind characterized by MPV2. The strong ascending motion caused by the increased cyclonic vorticity transferred the warm-moist air mass coming from the southeast of the rainfall area upward, and therefore, the torrential rain occurred. The conditional symmetric instability was the important instability mechanism for the torrential rain enhancement.