Abstract: Based on the available information and data about steel corrosion, the main factors influencing the decaying resistance of steel gate structural members are analyzed and a law of corrosion is derived. A model of decaying resistance of gate structural members is proposed. The reliability indices of bending structural member are analyzed and calculated with the consideration of determined )(tj or random variable )(tj and time-invariant loads or time-variant loads. The present research work can serve as the basis of the service life prediction of existing gate structures as well as the basis of maintenance and consolidation of existing gate structures. It is believe that this is the first effort in China addressing the problem.