Grinding force is a crucial parameter in the grinding process, as it is intricately linked to factors such as workpiece surface roughness, grinding temperature, grinding specific energy, and grinding wheel service life. The proposed grinding force model takes into account the material softening effect resulting from ultrasonic vibration and the void cutting effect due to trajectory overlap. Consequently, based on the grinding wheel model featuring a random distribution of abrasive grains, the non-productive grinding area arising from void cutting between abrasive grains is considered, leading to the establishment of an actual grinding area model.Utilizing the refined Johnson-Cook constitutive equation and accounting for the material softening effect induced by ultrasonic vibration, an ultrasonic grinding force prediction model is developed. In conclusion, a comparison is drawn between the experiment results of ultrasonic grinding and the model's simulation results. The average relative error for tangential grinding force stands at 19.78%, while the average relative error for normal grinding force is 17.72%.