Abstract: It is important to achieve conservation or break-even calculations of water substances such as water vapour in global or regional numerical models where the lack of mass conservation may lead to spurious water vapour movements and excessive local precipitation. At present, the advection scheme used in CMA-MESO model is the PRM (Piece-wise Rational Method) scheme. Although this scheme has high accuracy and positive, definite shape retention and is able to achieve conservation in the global model, it is difficult to achieve conservation or break-even in the limited-area model due to the treatment of lateral boundaries in the limited-area model. In order to solve the conservation problem of the model advection scheme in a limited-area model, a new and simple limited-area model semi-Lagrangian scheme mass conservation method (Zero Lateral Flux, ZLF) with negligible computational cost has been developed and applied in the CMA-MESO model. In this study, the ideal experimental results show that the ZLF scheme has good conservation and conformality, and can better maintain the distribution of the physical quantity field and the conservation of strong discontinuous physical quantity fields. Then the scheme is added to the CMA-MESO model, and the results of actual case forecast experiments and continuous forecast experiments show that the ZLF scheme can suppress overestimated precipitation, reduce false precipitation forecasts, and significantly improve precipitation-falling area forecasts. For extreme rainstorms, the ZLF scheme has a very significant improvement effect on the forecast of precipitation magnitude and precipitation area. The ZLF scheme improves the water non-conservation problem of the CMA-MESO model (effectively) as well as the precipitation forecasting effect of the model.