The weight vector is introduced into the traditional principal component analysis（PCA）so as to improve the rapidity and accuracy of fault diagnosis on hydraulic driving system of shield cutterhead; and the formula of variableweightedprincipalcomponentanalysis (VWPCA)method is deduced.The model of cutterhead hydraulic driving system of earth pressure balance shield with diameter of 6 450 mm is established by software AMESim; and 12 variables and 6 faults are selected and simulated respectively. And then, the weight vectors of every fault can be obtained from the simulation data.As a result,the model of VWPCA method can be established to study the fault samples.The study results show that the contributions of every variable to different faults can be improved by variable weighting; the accuracy of system fault diagnosis by VWPCA method can be significantly improved by more than 50%.