Abstract: By use of the transplanted mesoscale model (MM4) from PSU/NCAR, a strong rainfall event during 26—27 June 1986 in Beijing-Tianjin-Heibei area is simulated. The results show that the reduction in wind speed near the convective region in upper levels and passage through the rainfall center of the intensifying LLJ played crucial role in the event. The mergence of meso-low which convergence region ahead of the LLJ, feedback of latent heat release, and fluxes of heat and moisture from the underlying surface were also responsible for the event whereas the northwest low did not contribute much to precipitation.