Abstract: In the process of shield tunnelling, synchronous grouting for shield tail gap is a crucial process to alleviate problems caused by the tunnelling, such as ground loss, tunnel deformation and ground subsidence. This paper offers a brief overview of the development of synchronous grouting in shield tunnelling and a brief discussion on several core issues of such grouting method, including the selection of grout materials, the control of construction parameters, the mechanism of grout diffusion, the action of the grout on the shield segments and rock-soil masses, and the evaluation of the grouting effect. For different core issues, the focused analytical method is different (indoor model test, field measurement, theoretical analysis and numerical simulation). Based on the status-quo of relevant studies,the directions for future research are proposed from different perspectives with a view to providing useful guidance for relevant researchers and engineers.