Abstract: In AC motor drive system with multi motor, the number of switching devices will increase exponentially with the number of motors. This will bring a series of challenges to the design of the drive system. Based on this consideration, the leg-sharing motor drive system has attached more attentions. The leg-sharing motor drive system connects one switching device to two or more windings. It can effectively reduce the number of switching devices, but introduce challenges including decreased control freedom. The common topologies of the leg-sharing motor drive system are summarized, including the five-leg dual motor system, the four-leg dual motor system, the three-leg dual motor system, and half centralized open winding motor systems. The structural characteristics and power supply characteristics of each topology are analyzed. Afterwards, the research directions of control strategies are summarized for each topology. Finally, the future development direction of the leg-sharing motor drive system is discussed and anticipated.