Abstract: Based on the Smolarkiewicz's scheme (1983),this paper proposes a new positively definite advection scheme which has a unconditional stibility, simple form, small implicit diffusion and clear physical sense. It can be easily applied to the multidimensional model. In this paper author compares the present scheme and some other known positive definite scheme by using a analytic test. Finally, the scheme is applied to the moisture equation in the FLM (the fine-mesh limited regional model of National Meteorological Center) and the result of the experiment indicates that the new scheme can avoid the problem of spurious generation of negative moisture and improve the 24-hour forecasting precipatation field.