Abstract: The resistance probability model is the foundation for study on time-dependent reliability of bridge. Material aging and damage of existing reinforced concrete bridges are very complex processes which make the resistance random, fuzzy and time-variant, therefore the resistance development is a fuzzy stochastic process. Some uncertain factors influencing resistance are analyzed in this paper. Fuzzy random time-varying probability models for concrete strength, reinforcement strength and reinforcement cross section area considering durability damage in service life of existing reinforced concrete bridges are created based on measured data and other information. Fuzzy random time-varying probability model of the resistance of bridge members without maintenance is deduced. The variations of mean value and standard deviation with time and the threshold value are presented. Detailed analytic process and results are introduced using a bending member as an example.