Nested grid experiments are made for the barotropic primitive equation by a one-way interaction method. The quasi-Lagranian difference scheme by space factorization is used for both fine and coarse grids and the interracial boundary conditions (Scheme 2)proposed by Liao Dongxian et al. Scheme 2 is in keeping with the said difference scheme. Experiments show that in the 24-hr fine grid forecasts by Scheme 2 the inflow and outflow in the system with the unstability at the outflow eliminated are better than those by the half-momentum scheme and the interracial boundary conditions directly provided for the fine grid by the course grid (Scheme 1). Scheme 2 and Scheme 1, when combined with the method of Davies’s "Relaxation Regions", become Scheme 4 and Scheme 3, respectively. The results are much the same as those by using Scheme 1 and Scheme 2. It is found that Scheme 4 is a little better than Scheme 2.