Abstract: With the ever-expanding size of depot ships，the problem of liquid sloshing in cargo tanks becomes increasingly highlighted. In order to provide reliable reference data during the design process of tank structures for large-scale depot ships，a calculation procedure of sloshing loads with high precision and numerical stability is proposed in this paper. This procedure uses the improved VOF method，namely the Youngs method，to reconstruct the free surface and incorporates partial cell parameters to deal with complex non-rectangle liquid tank boundaries. Experiments with different filling ratio were conducted，and the results obtained with this procedure and those with Hirt-Nichols method were compared. It has been found out that the method suggested here could improve the free surface simulation speed as well as the estimation accuracy of the internal velocity，acceleration and pressure. Also，a separate cell sensibility analysis successfully validates the method's reliability with coarse grids，which suggests that it could be also applied to the quick estimation of design sloshing loads.