Using nonhydrostatic mesoscale numerical model MM5V3 to conduct simula tion for 3 “YaAnTianLou" cases, special analysis is made to see the impact of bou ndary layer (BL) parameterization scheme MRF on the maximum intensity of rainfall and the distribution of rain area. The results show that MRF scheme has good for ecast effect, and can describe the zonalvertical circulation structure when ra instorm occurs in Ya'an; Under the condition of complex topography, the role of BL is very important, especially where the precipitation has obvious daily chang e.