The invention discloses an on-line checking method for the breaking current of breakers, which comprises the following steps: obtaining full-network measuring data from EMS (enhanced message service) in real time and establishing a power grid model; carrying out credibility evaluation on the full-network measuring data and maintaining the data qualified in the evaluation; arranging fault points in the power grid, respectively adopting dynamic and static calculation analyzing methods on each fault point, and obtaining the data of the short-circuit current under various short-circuit fault types through the calculation; calculating the short-circuit current passing through each breaker; comparing the obtained data of the short-circuit current passing through each breaker and the nominal breaking current, and transmitting the checking result and the corresponding short-circuit fault information to the EMS to alarm if the indexes of short-circuit current data of each breaker exceed those of the nominal breaking current; and otherwise, carrying out the checking calculation of next short-circuit fault type. The method can enhance the accuracy of the short-circuit current calculation result and enhances the reliability of the safe operation of the power grid, and the on-line checking and the real-time early warning of the breaking current of the breakers can be realized through the method.