Abstract: Numerical simulation is a key approach to solve sloshing problem. Based on Constrained Interpolation Profile (CIP) method, a finite differential method is developed to study two-dimensional incompressible Navier-Stokes equations in tank-fixed coordinate system. Flow field is solved by fractional step method and free surface is captured by Tangent of Hyperbola for INterface Capturing (THINC) scheme. Sloshing is simplified as a multiphase problem including water, air and solid. Sloshing in tank without and with a baffle is studied. Breaking of free surface, slamming and evolution of vortices can be simulated. The numerical results for surface elevation and pressure are in good agreements with experimental data. The results show that this method can be applied to simulate large amplitude sloshing problem, while the baffle can effectively reduce the amplitude of sloshing.