Bridge life cycle maintenance costs can be estimated more accurately if the deteriorating and maintaining process can be simulated objectively. This paper first proposed a reliabilitybased model for prediction of deterioration. The performance of bridge elements was quantified by the reliability index. A stochastic approach was then introduced and the probabilities for what action should be taken at any time point can be determined. Afterwards, the costs associated with different maintaining actions were summarized from historical records. Thus, the maintaining cost for a bridge element can be taken as the sum of costs for all actions incurred over its lifespan. Monte Carlo Simulation (MCS) was finally applied to generate the probability distribution of cost estimation. Expansion joint was taken as an example to demonstrate the framework of the model. Likewise, the proposed model can be applied to all bridge elements and in turn, evaluate the maintenance cost for a whole bridge.