Abstract: In order to investigate the temperature and stress distribution of laser multi-track overlapping transformation hardening of vermicular graphite cast iron and analyze the influence of the change of overlap rate on the thermo-mechanical coupling field, the laser lap process was simulated by finite element method, and the distributions of temperature field,hardened zone, temper softening zone and stress field at overlap rates of 0, 10%, 20%, 40% and 70% were obtained. The results show that as the laser lap increases, the temperature of each scanning track gradually increases, and the center of the overlapping area between the subsequent tracks undergoes secondary hardening. With the increase of the overlap rate, the peak temperature of the overlapping first decreases and then rises. The peak temperature is lowest when the overlap rate is 40%. The temper softening zone is close to the previous quenching zone of the overlapping area, which locates at the edge of the overlapping zone. The temper softening zone increases as the overlap rate increases. After the lap treatment, the residual stress in the parallel and vertical laser scanning directions of the material surface is much larger than the residual stress value in the depth direction. With the increase of the overlap rate, the peak residual stress first increases and then decreases, and the residual stress value is highest when the overlap rate is 40%.