The long-term performance of simply supported Prestressed Concrete (PC) girder bridges exhibits dynamic characteristics because of concrete shrinkage, concrete creep, resistance degradation and vehicle load flows. The vehicle loads are non-stationary and random, which interacts with concrete shrinkage, concrete creep and resistance degradation to cause dynamic changes of bridge internal force and deformation, further, bridge dynamic reliability occurs. This study presented a reasonable method for calculating the time-varying reliability of simply supported PC girder bridges under the effects of traffic loads and concrete shrinkage creep. Stochastic truck-load models were simulated based on site-specific weigh-in-motion measurements, then the internal forces of the bridge were calculated when the mean value of vehicle loads increases by 1% per year. Considering the resistance degradation and load effect increase, the PC bridge reliability for serviceability limit state and capacity-carrying ultimate state were analyzed using first-passage probability method and Monte-Carlo method, respectively. The accuracy of the proposed method was verified by comparison. The evaluation results show that the failure probability including concrete shrinkage and creep has increased significantly, creep is affected by the bridge span and the number of main girders, and the reliability assessment results are safer for bridges with smaller spans.