A dynamic reliability analysis method for the existing RC bridge under fuzzy detective data was proposed since the statistical property of variables is unable to be determined based on the defective and incomplete detective data.The decrease of bearing capacity induced due to reinforcement corrosion under chloride environment was considered.The membership function was used to describe the defective information.The fuzzy variable was transformed into equivalent random variable based on equal probability principle during the course of reliability analysis.And then the dynamic reliability index of a actual bridge was assessed based on the Mont Carlo sampling method with arbitrary probability density function.The results show that the mean of fuzzy detective data has relatively great influence on the steel reinforcement area loss.Among them

the mean of concrete cover is the most significant

and has a strong effect on the dynamic reliability analysis.The decrease of steel reinforcement area is insensitive in the fuzzy ranges of variables.More attention should be paid to the mean of membership function at the process of determining the membership function.