Abstract: Silicon wafer grinding thinning is a material removal method different from conventional grinding. During grinding, the silicon wafer and the grinding wheel rotate simultaneously, and the grinding wheel feeds into the silicon wafer to remove excess material. The grinding force is a determinative factor on the grinding quality. There is no theoretical model of grinding force in silicon wafer self-rotating grinding yet. To develop the grinding force model, the grinding mechanism of silicon wafer self-rotating grinding was studied, and the grinding force was divided into a sliding force and a chip formation force. By considering the grain trajectory during grinding, the sliding force and the chip formation force of single abrasive grain on normal and tangential directions were established. Subsequently, based on the number of effective cutting grains, the total grinding force model was established. In this model, the influence of processing parameters, geometry parameters and material properties of silicon wafer and grinding wheel were comprehensively considered. Nine sets of grinding parameters were adopted into the model to study the effects of feed rate, wafer speed and wheel speed on the grinding force. Meanwhile, the effects of crystalline orientation were discussed, and the distribution of grinding force along radius on silicon wafer surface was also analyzed.