Abstract: The detail diagnostic analyses are made on two cases of Monsoon Depression over Southern China Sea by using FGGE3B data (no initialization),the diagnostic balance model (Krishnamurti, 1968) and the cumulus parameterization scheme (Kuo, 1974).The vertical circulation evolution of the Depression in the process of its genesis and development is contrasted in both cases, with and without diabatic heating. Meanwhile the studies are also made for the contribulion of latent heat to the vertical circulation. The results show that the largescale heating effect only plays a main role to the initial vertical motion field, and the cumulus heating effect is a main factor to the strengthening and maintaining of the Depression vertical circulation.