A simulation of typical weather event about meso-scale lows occurred in PBL over the North-China Plains and a series of its sensitivity experiments are carried out by using PSU/NCAR’s MM4 mesoscale model,which examines the MM4’s forecast capability for the meso-scale systems in PBL.It analyzes the impact of angles between airflow direction,mountain axis,and warm(cold) advection on the mesolow in North China by adjusting the matched patterns of terrain with wind,temperature and pressure fields.The result shows that the bigger the angle with a warm (or weak cold) advection in the lower layer,the more favourable for the generation of the macro-scale circulation,which play an important role in generating the mesolow,are put forward in line with the observed weather facts and the result of modelling tests.