Abstract: The forming mechanism of trapezoidal thread shafts was proposed by analyzing the forming process of teeth shape and the characteristic of metal flow. A die of cross wedge rolling was designed in consideration of the instantaneous variation of helix angle and the variation of teeth cross-section. The rolling process of trapezoidal thread shafts in cross wedge rolling was simulated with the finite element software Deform- 3D, and trapezoidal thread shafts with high precision were obtained. Radial and axial displacement variations in different sections of the rolled pieces were analyzed in detail by tracking multiple points on the rolled pieces using the tracking function of the finite element method. The metal flow law at different positions on the rolled piece was found out. The trapezoidal teeth profile rolled in rolling experiments performed by using the simulating parameters is similar to that calculated by the simulation software. Simulation and experiment results show that trapezoidal thread shafts with precise shape can be rolled by using the corresponding helix angle of the die to the instantaneous rolling radius.