At present Sola-Vof is the popular method in simulating mould filling of casting but it is difficult to exert the boundary conditions upon the free surface of liquid by Vof. The above difficulty is overcome at all by calculating the fluid flow field of coupled gas with liquid phase as a single phase N-S equation using conservative scalar method. But in this circumstance there exists the trouble with the numerical divergence caused from large variations across the interface in coping with the interface of gas/liquid. The Simple scheme has to be reconstructed according to Van-leer scheme. The experiments were conducted by hydraulic simulation for filling large plate in counter-gravity mould

and the simulating results agreed well with the experimental results.