Grinding is an essential gear finishing method. Grinding force analysis and prediction are critical to understand grinding mechanisms. By using a geometry model for gear form grinding and surface grinding mechanisms, a theoretical model was established to calculate the gear form grinding force. By considering the complete tooth depth engagement between tooth grooves and wheel profiles during form grinding, three segments of the involute, transition arc and tooth bottom line, which were included in complete tooth groove profiles, were analysed using the model. Contact relations among the normal grinding depth, wheel equivalent radius, wheel linear velocity and wheel profile were obtained. In addition, grinding experiments were outperformed on the basis of the single tooth, and the unknown coefficients of the form grinding force calculation model were acquired. The effects of the grinding depth, feed speed and grinding speed on grinding force were analysed using the grinding force model. The comparison of the predicted values of the form grinding force model with the experimental results, indicated that the relative errors of tangential and normal grinding forces are within ±10% and ±12%, respectively. The results confirmed the accuracy of gear form grinding force calculation model. These findings play a key role in parameter optimisation during gear form grinding.