This article introduced the research status of the physics of coupling zone in Hall thrusters. The coupling zone is the area that links hollow cathode and Hall thruster channel. It determines the electron parameters on the inlet of the channel and the discharge characteristics of the hollow cathode. With negative-gradient weak magnetic field in this area, the local physics are highly complicated. The article chose four different facets to discuss the parameter distribution and influencing factors of this area:the transport of seed electrons towards the anode, the process of ion beam neutralization, the E×B drift of plasma bridge electrons and the hollow cathode discharge in coupling environment. By summarizing the characteristics of this area, the difficulties and shortcomings of current studies were analyzed and suggestions for further studies were given.