Axial ultrasonic vibration-assisted peripheral grinding (AUPG) has the major advantages of simultaneously improving the grinding quality and material removal rate compared with conventional grinding methods. In this study, a grinding force prediction model for the AUPG of Zerodur was developed to investigate the generation mechanism of the grinding force for guidance in practical engineering applications. Taking into consideration the material removal mechanism, material properties and vibration impact, the three primary grinding force components were first separately modelled, namely, the ductile removal force in the ductile removal phase, the brittle removal force in the brittle removal phase and the frictional force of the friction process. The critical uncut chip thickness and maximum uncut chip thickness were subsequently researched to define the two material removal modes in the AUPG of Zerodur, namely, the ductile removal mode and the mixture of brittle and ductile removal mode. The grinding force models of these two material removal modes were developed using effective grinding force component models. The instantaneous variation of the grinding force with time and space was also analysed to derive models of the final time-averaged normal force, tangential force and axial force. Finally, grinding experiments were performed, the results of which showed that the prediction errors of the developed model were only 7.37 and 11.53% for the normal and tangential grinding forces, respectively. The axial ultrasonic vibration was also determined to reduce the surface roughness by 18.0% compared with conventional grinding, while the normal and tangential forces were reduced by 27.31 and 22.52%, respectively. This indicates that AUPG affords a significantly improved grinding surface quality. The developed model enables an understanding of the comprehensive mechanism of AUPG and provides a basis for the development of the grinding force models of the other brittle materials.