In order to solve bad roll stability problem of partially filled tanker in the process of steering, the liquid sloshing equivalent mechanical model and the partially filled tanker vehicle motion model were developed. Two models were coupled by dynamics of solid fluid interaction. Five different size proportions of elliptical tankers cross section were selected to simulate, it is concluded that the tanker has better roll stability because it has minimum sloshing force and moment, when long axis (2a) and short axis (2b) of the elliptical is the ratio of 1.5. The results provide technical support for the tanker’s driving roll stability research and vehicle design.