The nonlinear viscous flow generated from forced heaving oscillation of 2D floating body in calm water is carried out numerically using Improved Meshless Local Petrov-Galerkin (IMLPGR) method based on Rankine Source function. In the present particle-based method, the gradient calculation has been improved using ghost particle method. However, for estimating pressure, only single layer of the boundary particles are used. This is the first paper to extend the application of the IMLPGR for heave oscillations of the floating body. Simulations are carried out for vertical oscillation of rectangular shaped mono hull and twin hull. Hydrodynamics of these hulls for various amplitude and frequency of oscillations are performed and the numerical results agree well with existing literature results. Copyright © 2017 by the International Society of Offshore and Polar Engineers (ISOPE).