Abstract: Authers have studied the transformation processes of cold air over land in East Asia for eight cases which occurred in different months of 1981.First, the surface eddy sensible and latent heat fluxes, and drag coefficient were estimated according to the approach of similarity theory. Then, the apparent heat source, the apparent moisture sink,and solar and long-wave radiative heating(or cooling) were further calculated through the budget method and physical parameterization algorithm. It has been found that the cold air immediately starts the transformation process over land once it moves away from its region of origin. In winter, the degree of transformation of cold air mass gradually intensified as it travelled southeastward. While arriving in the ocean, the cold air mass underwent the most significant transformation process. In summer, the most vigorous transformation of thermal and moisture fields was observed in North China and Mongolian region, with much greater intensity than that in winter.