Abstract: In order to make the error of forecasted area casued by lateral boundary processing as far as possible to achieve the minimum in the forecast period,we should choose the better lateral boundary processing method.Thus,three kind of lateral boundary simulation schemes are nested to the barotropic primitive equations:Fixed boundary condition;Sponge boundary condition;Non-gradient boundary condition.In order to explore the issue of the buffer zone,has designed two kind of plans:Plan A:After (38.75N,78.75E) as the central region 60120 grid point is simulated,then outputed except most outside 5 results.Plan B:After (38.75N,78.75E) as the central region 50110 grid point is simulated,then direct outputed result.Compared with two kind of plan is nested different side boundary to barotropic primitive equation pattern simulation identical region geopotential height field influence.The results indicated that ①A plan is nested fixed boundary condition and sponge boundary condition are all better than non-gradient boundary condition in forecast effect,which best is the sponge boundary condition.②B plan is nested fixed boundary condition and sponge boundary condition is all better than non-gradient boundary condition,which best is the fixed boundary condition.③Plan A is better than plan B.