The invention discloses a high-voltage overhead transmission line dirt detection method. Voltage and current data detected on site and generalized correlation coefficients of a sample dataset are calculated, and the dirt situation of an actual overhead line can be judged according to the dirt situation corresponding to the sample data with maximum correlation coefficient. According to the high-voltage overhead transmission line dirt detection method, primary wiring and secondary wiring of the line are not needed to be changed, new additional devices are not needed, and line dirt detection can be achieved only by using voltage and current provided by data acquisition units at two end of the existing line as signal sources. The high-voltage overhead transmission line dirt detection method is simple and practical and has high operability and universality, can achieve offline detection and online detection, can independently form a detection device and system and can also serve as an important constituent part of a whole transmission line intelligent monitoring system.