The invention provides a control method and apparatus for an ultra-high-voltage direct current participated strong direct current and weak alternating current power grid safety defense line. Weather the strong direct current and weak alternating current power grid suffers from transient state power angle instability or not is judged firstly; if so, each ultra-high-voltage direct current participated strong direct current and weak alternating current power grid-comprising safety defense line is determined; and the strong direct current and weak alternating current power grid is controlled according to each ultra-high-voltage direct current participated strong direct current and weak alternating current power grid safety defense line. By virtue of the three safety defense lines of the ultra-high-voltage direct current participated strong direct current and weak alternating current power grid provided by the invention, generator tripping, load shedding, low frequency load decreasing and high-cycle generator tripping in a direct current power pre-control strategy, a direct current power emergency modulation strategy and a safe and stable control strategy are taken into consideration, so that the safety defense effectiveness of the strong direct current and weak alternating current power grid is greatly improved; and in addition, the application environment of the ultra-high-voltage direct current participated strong direct current and weak alternating current power grid safety defense lines, the control strategy of each safety defense line, and the mutually matched strategies of the three safety defense lines are determined, thereby a convenient and effective approach is provided for the strong direct current and weak alternating current power grid safety defense.