The insulators leakage current in transmission line can be used to characterize the filth degree of insulator surface and its accurate measurement is very important. An on-line monitor platform for insulators leakage current is introduced. Then a new multiscale self-correcting method for insulators leakage current is put forward. In this method, the leakage current information is decomposed based on multilayer and multiscale theory to gain each scale detailed signal and smooth the information in the coarsest scale at first. Furthermore, each scale detailed signal is decomposed once again and processed at different thresholds. Afterwards, the signal is reconstructed. The reconstructed detailed signal and the coarsest scale smoothed information are filtered using Kalman filter. In the end, the optimal detailed signal and the smoothed detailed signal are reconstructed and the signal is optimally estimated in the finest scale. Finally, the method was been applied to safety monitoring for a real transmission line. The results show that, compared with traditional Kalman filter method, the precision of new method raises 27%. This method has the characteristics of strong denoising ability and good robustness. It can be applied to the similar complex situation.