Based on the contact characteristics of helical surfaces and the coexistence of rolling and sliding at the screw-roller interface, a forecast model of thread pair using Archard wear theory is proposed. To obtain the wear depth and the wear volume of the screw raceway in the whole effective stroke, a test rig of thread wear is developed to obtain the wear rate that can be used to fit the values of the stress index and speed index. The area coefficient is further deduced to reflect the real wear condition. The calculation method of the relative sliding speed, coordinate transformation and load distribution are provided, the finite element (FE) model is established, and the transient dynamic simulation of thread wear is implemented to verify the correctness of the wear model. The relative error is less than 9% between the FE model and proposed model by comparing the wear depths and wear volumes, which indicates the wear model proposed in this paper is valid and can be used to forecast the thread wear of the PRSM. Finally, the wear behavior of the thread pair is preliminarily discussed based on the FE model.