Abstract: A fault diagnosis method based on multi-fractal detrend fluctuation analysis (MF-DFA) and support vector machine was proposed, aiming at complex and nolinear in nolinerar analog circuit faults.Two content are researched which include the multifractal detrend fluctuation analysis and fault diagnosis based on multifractal spectrum features.Firstly, output voltage signals from the test node are obtained and the fault feature vectors are extracted by multifractal detrend fluctuation analysis method.Then the features are input into the one-against-all multiclass SVM to identify the different fault cases.Fault diagnosis simulation experimental results on Duffing chaos circuit shows the effetiveness of the proposed method.