Abstract: A numerical method was applied to a S2,stream-surface streamline curvature approach to calculate the fan/compressor performance.The flow field around the splitter lip was found by calculating the potential flow field along the splitter surface and subsequent turbulent boundary layer analysis.The potential flow field was found by using a singularity method.A fan/compressor component was selected as an example to investigate the splitter lip effects on performance of fan/compressor system.A number of different splitter lip geometric parameters,such as the axial location,shape of splitter lip meanline and nose was considered and their effects on the fan/compressor performance were discussed.A proper selection of geometric parameters will be a great help to controll effectively the boundary layer flow on splitter lip surface.As a result,the boundary layer separation can be delayed and the choking can be improved.