The void is one of the unavoidable defects in the square billet. Due to the larger size of the generous square billet, the closing process of void is very difficult. Therefore, the thermal-mechanical coupling model of rolled parts with void in the rolling process was established by finite element software Deform, and the local subdivision of mesh for the void part was conducted to mainly simulate the void closure behavior in reciprocating transverse rolling process. By simulating the evolution conditions of the void with the diameter of Φ9-Φ12 mm, it is found that the smaller the void is, the easier it is to close. In addition, by analyzing the evolution laws of the void at different positions, it can be known that the closer to the surface of rolled parts, the greater the impact of rolling force on the void closure. When the void is close to the surface, the void closure is not only affected by the rolling force, but also by the temperature. The voids at a distance of 102 mm from the centerline are closed quickly when the equivalent strain is less than 0.3, and when the equivalent strain is greater than 0.3, the voids are closed slowly due to the decreasing of temperature around the voids. In summary, reducing the number of steel transfers, increasing the rolling force and controlling the temperature of rolled parts are beneficial to the void closure in the reciprocating rolling process of generous square bille.