Abstract: Self rotating grinding with cup diamond wheel is a typical ultra precision grinding process for silicon wafer.The simulation model based on the force of micro contact between wheel micro unit and silicon wafer is established from the stable ductile grinding process.Micro contact process of self rotating grinding is simulated using the analysis software LS-DYNA.The stress-strain results between silicon wafer and wheel micro unit are analyzed using finite element method.The results show that there exist critical displacements and loads of elastic-plastic and plastic-brittle transitions when processing silicon wafer.During the tangential sliding in plastic zone,plastic grooves and uplifts appear on silicon surface.Wear of wheel micro unit can be judged based on the simulation data.The research provides support for wafer grinding and wheel wear mechanism.