The influencing information of structural resistance cannot be exactly inspected due to limitation of the experimental means, time and space. The study must be conducted by incomplete information and the uncertainty is enhanced. The uncertainty consists of fuzziness, randomness, and faultiness of knowledge. The faultiness of knowledge is the weak uncertainty, and can be incorporated into fuzziness and randomness. A novel probabilistic analysis method of corrosion-induced resistance degradation subject to fuzziness and randomness is developed in this paper. The reinforcing bar corrosion is induced by chloride ion attack in reinforced concrete (RC) bridge. The relationship between steel area corrosion rate and yield strength is presented based on the experimental investigation on mechanical property of corroded reinforcement. The fuzzy time-variant probabilistic analysis of resistance degradation is illustrated by an example problem of RC bridge beam. The result can be used to time-variant reliability-based evaluation for reinforced concrete.