Abstract: In this paper,the influence of meso-scale stationary lee wave on the genesis and development of synoptic system is discussed.A simplified mathematical model including the role of Dabieshan is established for numerical calculation,the result indicates:when basic f1ow U equals to 101m/s,stratification parameter N equals to 103S-1 and the ratio of U to N approximates 3×103-4×103,a kind of equivalent-barotropic lee wave could appear,its wavelength approximates U/f (f is Coriolis parameter-104s-1).Then a practical case of heavy rain is analysed by using above conclusion to point out during Jianghuai meiyu period,when migarating rainstorm moves to certain position of Dabieshan's stationary lee wave,the precipitation could intensify.