Aiming at solving the defects of risk priority number (RPN) in mathematics, ingredients and research object, classic RPN method is analyzed. And an improved RPN method facing to intermittent fault of electronic system is presented. This method estimates failure times O by fivestate Markov mode, the correlation and influence analysis of fault location, mechanism and mode are carried out by DEMATEL method, and the results which have the same sequence number in RPN first sorting are sorted by Mahalanobis distance. This method solves the problems well, for instance, classic RPN value is not a continuous integer, RPN result is sensitive to fractional changes of three key information factor S, O and D. The improved RPN computing model is applied to analyze intermittent fault case of a sea based equipment, which can get objective risks prioritization of different intermittent faults, and a good result is obtained.