Abstract: Based on the probability model of wire corrosion initiation and the probability model of corrosion expansion, the time-dependent failure probability model for a corroded parallel wire cable is established. According to characteristics of a wire-corrosion probability tree formed by probability in each consecutive inspection period, the branch and bound method was introduced to calculate the corrosion probability, solving the key problems of the exponential growth in computational amount. The model parameters and an example of cable's failure probability were investigated. In premise of the correct statistical estimation on all model parameters, the results demonstrate that the model can predict the number of corroded wires with their probability in any detection period for a cable in service, and calculate the total amount of wire corrosion area. Moreover, the model can be used to analyze the time-dependent cable failure probability. The proposed model is an exploratory research on the cable corrosion failure problem, thus it has a certain reference value for the inspection and evaluation on stay-cables.