Abstract: The issue of safety and economy should be considered in the repairing and strengthening of existing bridges. The strategy on repair and strengthening of existing bridges based on time-dependent reliability has been analyzed with the maximum expected benefit or the minimum expected cost of failure consequence as the objective function. A practical application of risk-ranking decision is illustrated herein based on updated inspection information with the bridge survival age 35. The effects of improvement of live load and difference of repair methods on time-dependent reliability of existing bridges are studied. The decision method can be used in real project, with the cost of failure consequence and the risk of failure considered. It has certain reference value in the repair and strengthening decision of existing bridges.