The invention relates to a method for maintaining and repairing a 10kV protecting device, in particularly to a method for on-line precision calibration of the 10kV protecting device. The method for on-line precision calibration of the 10kV protecting device is characterized in that relay protecting equipment is compared according to the standards that the accuracy grade of a CT for measuring and controlling is higher than the accuracy grade for relay protecting, and the collecting precision of data collected by measuring and controlling equipment is high for the reason of a current transformer. Calibration modules are integrated in a CPU of a relay protecting device, when an instruction of a dispatching monitoring system is received, the replay protecting equipment can be compared through CT sampling, the measuring and monitoring equipment can be compared through CT sampling, and the sampling precision of the relay protecting equipment can be calculated automatically. Thus, power outage processing does not need to be conducted on the protecting device, and the reliability of operation of a power grid is guaranteed. Moreover, automation is achieved in the whole processing process, tedious operation such as power outage operation and simulation current connecting is of no need, and therefore the calibration method is simple, reliable, and high in efficiency.