The invention discloses a high-precision on-line detection method for a contact wear rate of a circuit breaker. The method comprises the following steps of: collecting the on/off times of the circuitbreaker under different environmental temperature parameters and different voltage values, and performing the curve fitting of the collected data to obtain the temperature influence factors and the voltage influence factors. The contact wear rate detection of the continuous large-area current domain is realized through the pre-processing and curve fitting of the circuit breaker on-off life monitoring data, and the accuracy of curve fitting is improved by the evaluation method of curve fitting errors. The data curve fitting function of the contact wear rate of the circuit breaker needs furtherdiscretization processing, and the discretization processing comprehensively considers the storage space and system calculation amount of the system processor. Finally, the circuit breaker controllersystem uses a binary table-searching method to realize the fast online table-searching operation of the circuit breaker controller on the contact wear rate. According to the high-precision, continuous, wide range on-line detection technology for the contact wear rate, the contact wear rate detection of the circuit breaker in the continuous large-scale current domain can be realized, and the requirements for the on-line health detection of the equipment through the low-voltage intelligent power distribution technology and the intelligent operation and maintenance of the equipment finally can bemet.