Inconel 718 nickel-based superalloy is a representative hard-to-cut material with excellent comprehensive thermomechanical properties, and it has marked foreground in the field of aerospace engineering. The ultrasonic vibration-assisted grinding is an advanced machining technology for improving the efficiency and surface quality. However, the heterogeneity of abrasive grits on the grinding wheel surface and the use of ultrasonic vibration increase the complexity of the material removal mechanism. In the study, an analytical grinding force model was developed under the consideration of abrasive grit heterogeneity and ultrasonic vibration. The influence of multiple grinding path intersects and the interaction effect between undeformed chip thickness and quantity of effective abrasive grits were revealed. The results indicate that the use of ultrasonic vibration is helpful to keep the grinding temperature steady blow 100 ℃ with an increase in maximum material removal rate by 20%. The maximum undeformed chip thickness has negative linear relationship with the minimum exposure height of effective abrasive grits, the parameters in the relationship are mainly related to the grinding wheel. The performance of ultrasonic vibration is better under the condition of deeper grinding depth and larger ultrasonic amplitude, resulting from the increase in workpiece infeed distance within the interval of abrasive grit cutting and the increase in grinding arc length. The average error and maximum error of the model are 5.2% and 14.9%, respectively. The grinding force can be reduced by 30% at most when the ultrasonic amplitude is 8 μm.