Induction motor load, which is contained in the growing load center of power grid, brings serious risk of voltage instability and even collapse to power system due to its highly nonlinear and dynamic characteristics. By studying the load characteristics of induction motors, this paper analyses the relationship between induction motors and power system stability. At the same time, based on the controllable characteristics of power transmission in flexible DC system, a flexible emergency support control strategy is studied. The switching power between AC and DC lines is adjusted by changing the control command value appropriately, so as to realize load and system stability. Finally, a local AC/DC system model of a city is built on the platform of PSCAD/EMTDC, and simulation analysis is carried out for different load ratios of induction motors. It is proved that the control strategy of flexible DC system can effectively improve the load stability level of induction motor in power grid.