The fluid structure interaction(FSI)is a complex nonlinear problem.In this paper,a new scheme of FSI is presented based on the incompressible material point method(iMPM),in which the fluid domain is simulated by iMPM while the solid domain is represented by the material point method(MPM).The iMPM is an extension to the traditional MPM proposed by our team for fully incompressible fluid flow with free surface,in which the pressure is solved from the global Poisson equation rather than from the local particle strain increment as that in MPM.This augmented method avoids the “crossing-noise” problem inherent in MPM,and is suitable for low speed flow problem with free surface.