Abstract: In order to solve the problem of preload loss caused by machining error, raceway wear and other factors, the Nord- locking feature is applied to the design of ball screws, and a new design of self pre-tighten ball screws is proposed. The preload mechanism is composed of left and right wedging washers. The left and right washers make the two nuts produce relative displacement in the axial direction, thus generate the axial preload. At the same time, the wedging effect of the left and right washers makes the washers self-adjust according to the preload, so as to ensure that the preload remains unchanged. Through theoretical calculation and simulation analysis, the structural design of wedge-shaped pre-tighten washer is carried out, and the key structural parameters are determined. On the basis of SolidWorks for geometric modeling, the transient dynamics of the new preload ball screws is analyzed by using the finite element software, and the modal comparison between the new ball screws and the traditional ball screws is carried out. The results show that this new type of ball screws is expected to be a kind of high reliability and long life ball screws with good application prospects in engineering.