Abstract: To predict fatigue life for sliding screw of adjustment mechanism of seedling box， the calculation formula of fatigue life was derived by the related theory and method. The rigid coupling model of adjustment mechanism was built with Adams and Ansys software. The real working condition of adjustment mechanism of seedling box was imitated and the axial load of screw was gained. The maximum Von Mises stress of thread was 188 MPa， which was analyzed by the finite element method based on Ansys software. The maximum Von Mises stress was less than strength limit of the material. Based on the initial conditions， fatigue life of thread was analyzed with Ansys/fesafe software. The results showed that the working life of sliding screw was 3 598 h and met the requirements of rice transplanter.

Key words: adjustable spacing transplanter；seedling box, sliding screw, thread, fatigue life