Abstract: Grouting is frequently used to control and adjust the large transverse deformation of shield tunnels in clays. However, the grouting is usually performed based on the engineering experience. The control mechanism of grouting for the tunnel transverse deformation is not clear. In this paper, the method to simulate the performance of grouting through the resulted soil expansion is proposed and validated. The effect of grouting on the large transverse deformation of shield tunnels is investigated in terms of the change of tunnel diameter and joint movement using numerical simulation. The optimization is finally carried out through the parametric study. The researches indicate that the grouting can significantly reduce the tunnel transverse deformation and joint opening, and can also produce remarkable joint offset when the volumetric strain of ground caused by the grouting is larger than 3%. The grouting firstly causes rotation and then rigid movement of tunnel segements. Thereafter, the joint opening reduces more significantly due to the segmental rotation at the beginning of grouting. The joint offset increases significantly due to the rigid movement of tunnel segments when more grouting is injected.