The invention provides an electric power system cascading failure blocking method based on active minimum generator tripping, which is used for solving the problem of electric power system cascading failure caused by line overload in the prior art. A calculation method of the minimum generator tripping amount for blocking cascading failures is provided; meanwhile, by considering a power constraint, a load capacity constraint and a balance node adjustment speed constraint, a verification method for verifying the minimum generator tripping amount is provided; meanwhile, aiming at the condition that the minimum generator tripping amount does not meet the constraints, the invention provides a correction method of the minimum generator tripping amount. According to the method, the power control capability of the power supply in the power system can be utilized to the maximum extent, the power of the overload power transmission line is rapidly recovered, and the generator tripping and load shedding power is reduced as much as possible, so that cascading failures of the power system are effectively blocked, the blocking cost is reduced, and the power system stability is improved.