Amplitude threshold method has good recognition of large errors and ultra magnitude of the abnormal data in load history, while the gradient threshold method is effective in detecting the abnormal signals with small amplitude. Considering this characteristic, a method is provided to process the abnormal signals with the combined application of amplitude threshold method and gradient thres hold method, which is followed by the case of processing the load history of the transmission. Being efficient in eliminating the abnormal signals in load history with various probability contributions, this method avoids the inherent limit ations of assuming the sample data subjecting to a typical probability distribution in existed method. Hence, this method can eliminate the abnormal signals accurately.