With the formation of multi-infeed HVDC, the difficulty of security and stability control of the system increases. Serious ac/dc fault occurs, the commutation failure in multi-circuit HVDC power transmission system will bring the system risk of losing stability, therefore avoiding commutation failure in HVDC power transmission system and maintaining voltage stability of receiving end power grid, are currently important problems that receiving end power grid takes control measures need to be solved. The power grid characteristics of multi-infeed HVDC and influence factors that lead to communication failure are analyzed, and the control strategy of voltage instability that formation of multi-infeed HVDC leads to is put forward in the sight of the three defense lines. Based on the simulation of the actual power grid, the proposed control strategy can effectively reduce the risk of commutation failure in multi-circuit HVDC and improve the voltage stability level of receiving end power grid.