Abstract: Numerical prediction experiments are made by use of a p—σ incorporated coordinate system model with primitive equations and a case study of May 8, 1982 is analysed in some details. There are two kinds of experimental schemes. One is the moist adiabatic prediction scheme and the other is the diabatic heating scheme in which the latent heating from the vapour condensation is included. Besides there are also various diabatic physical processes induced by the land- sea distribution , the topography and the underlying surfaces with different physical properties. The focus of this paper is the comparisons and discussions of the diabatic heating effects on circulation and weather in the trpoical-subtropical regions. The results show that the diabatic heating effects on the upper level temperature and height fields are not very evident, but the effects on the low level fields are larger, especially large are the effects on the wind field in the boundary layer in the Bay of Bengal area and the region south of the Tibetan Plateau, the variation rate in the twoschemes reaches 100%. Omitting diabatic heating processes will result in the weakening of the Tibetan Heat Low, the cyclonic circulation and the convergence of the wind field, as well as the southwesterlies. For the precipitation amount and distribution, the precipitation area over the Bay of Bengal disappears and the amount in the coastal regions of East China and over the western Pacific decreases, even no precipitation takes place in the scheme without diabatic heating processes.