AbstractMoving particle semi‐implicit (MPS) method is one of the particle methods, which can be used to analyze incompressible free surface flow without surface tracking by a mesh or a scalar quantity. However, MPS causes unphysical numerical oscillation of pressure with high frequencies. We proposed a new formulation for the source term of Poisson equation of pressure. The proposed source term consists of three parts, one main part and two error‐compensating parts. With proper selection of the coefficients for the error‐compensating parts, we can suppress the unphysical pressure oscillation. Smoother pressure distributions are obtained in hydrostatic pressure and dam break problems. Copyright © 2010 John Wiley & Sons, Ltd.