The invention relates to a safety control measure quantity acquisition method in a DC layered access mode. According to the method, firstly, a smallest power adjustment quantity required by an out-of-limit line after a line N-2 fault is calculated, sensitivity of layered access DC high and low end converter powers for the out-of-limit line is respectively calculated, the DC high and low end converter powers are considered to realize reduction simultaneously, a DC power adjustment quantity is calculated in combination with a DC dual-pole power control mode, one or two blocking high and low end converters are considered, whether the out-of-limit line power is in a limit value scope is calculated, and the DC safety control measure quantity is lastly calculated. The method is advantaged in that the safety control measure quantity can be calculated in the DC layered access mode, flow out-of-limit problems of other lines after the line N-2 fault can be solved, the method can be applied to online analysis control and offline simulation analysis of an electric power system, and technical supports can be provided for power grid programming, construction and operation analysis personnel.