The invention discloses a method for determining the measure amount of a circuit breaker miss operation fault in a flexible direct current power grid. The method comprises the step that when a circuitbreaker on the front side or the rear side of a faulty direct current line in the flexible direct current power grid has the miss operation fault, the measure amount of the to-be-adjusted fault of aconverter and the direct current line is determined according to the monitored effective bit of the converter and the direct current line in the flexible direct current power grid and the unbalanced power of a system. The method for calculating the measure amount of the fault has the advantages of high speed, high efficiency and short delay, and can improve the safe and stable operation level of aflexible direct current power grid project to a certain extent.