Concrete carbonation and rebar corrosion are two main processes accounting for the life cycle operational performance degradation for reinforced concrete (RC) bridges.This paper proposes the analyzing model and procedure for the evaluation of vehicle carrying safety of a RC grillage highway narrow bridge concerning concrete carbonation and rebar corrosion in its service life.Lumped plastic hinge model for the grillage beam components and vehicle load incremental methods for bridge plastic limit state analysis are adopted to analyze bridge vehicle carrying capacity considering material deterioration.Sensitivity analysis is conducted to check the key influential parameters which will accelerate structural performance degradation process.Monte Carlo simulation is employed to analyze bridge performance concerning uncertainties.Structural reliability index is computed to track structure life cycle safety degradation.Figure 1 is the life cycle bridge capacity degradation curve for the given bridge.