The Smoothed Particle Hydrodynamics (SPH) method has become one of the most promising methods for violent wave impact simulations. In this paper, the incompressible SPH (ISPH) method will be used to simulate liquid sloshing in a 2D tank with complex baffles. Firstly, the numerical model is validated against the experimental results and the simulations from commercial CFD software STAR-CCM+ for a sloshing tank without any baffle. Then various sloshing tanks are simulated under different conditions to analyze the influence of the excitation frequency and baffle configuration. The results show that the complex baffles can significantly influence the impact pressures on the wall caused by the violent sloshing, and the relevant analysis can help find the engineering solutions to effectively suppress the problem. The main purpose of the paper is to study the practical importance of this effect.