The traditional grid fault diagnoses are almost based on digital information,but there are some disadvantages of these diagnoses,such as the informationis always uncertain and unbelievable, which are susceptible to errors even come to wrong conclusion.The analogue information is about the transient and the wave of current and so on. The analogue information would be transformed to wavelet fault characteristics through the wavelet analysis.According to current distribution characteristics of grid, improved wavelet analysis. Set up IEEE39 nodes simulation ,and prove the correctness of this method,the obtain the wavelet fault degree of each incredulous line.