The heavy rain occurred in the northwestern area of Beijing on the night of June 24,2002 is a severe orographic rainfall.The heavy rain under the conditions there were two inverse temperature layers in the middle and low troposphere is affected by the reciprocity between mLLJ and Beijing terrain.The generation and development of mLLJ in boundary layer is caused by deflective east wind in the low layer,the inner boundary effect in the dry and wet process,the latent heat release of strong rainfall and the reciprocity of them.