In this paper pressure source terms proposed by different researcher are compared in term of pressure stability. In Moving Particle Semi-Implicit (MPS) method, the pressure error is compensated back into pressure Poisson equation as source term in order to enforce the incompressibility. However the non physical pressure fluctuation still remains an open problem in MPS method. In present study the hydrostatic model is used as example to study the pressure stability for each of the pressure source terms. The pressure at the fixed point over time is plotted and the fluctuation from the theoretical pressure is discussed.