Abstract: A split explicit integration of 5-level primitive equation model in modified σ-coordinate is investigated. The governing equations are divided into two process: advection and adjustment process. The former equations are written in the form as(12)-(14), and the latter in the form as(7)-(11). The Euler-Backward Scheme is used in the advection process, and the Forward-Backward scheme is used in the ad justment process.The above scheme has been successfully integrated up to 15 days for an example, and the computation time is only 40% of that of the explicit scheme.