Abstract: Considering the unadvanced design and analysis of reliability of regulation structures at present, and based on prototype observation and flume experiments， the damage of the spur dike caused by water may be approximately regarded as the damage caused by alternate cyclic action of various flood peak discharge. On this basis， the failure probability of the spur dike can be described by the Weibull distribution model with three parameters. Based on the theory of equivalence volume， a formula for evaluating the residual life of the spur dike after the flood action is deduced. The analysis results show that the calculated results fit the real data well and can be used to calculate the residual life of the spur dike， which is a good reference to the project design and maintenance.