To ensure that safety level can be maintained within the acceptable range, civil aviation aircraft need to carry out risk assessment in the continued airworthiness stage. This paper is based on the Transport Aircraft Risk Assessment Method (TARAM) and the risk criteria, by considering different crack sizes, and giving the calculation method of fleet risk value based on the fleet fault number, critical crack and characteristic life. And taking the fatigue crack of the fuselage supercharging boundary structure as an example for ongoing safety risk assessment to calculate the risk level of the event, and the time limit of corrective action implementation. And the implementation time limit of corrective measures was validated by individual risk within time limit using corrective actions. Since the results show that the individual risk is below the risk threshold, it can be concluded that the corrective measures and implementation time limit formulated in this article meet the continuous safety requirements of the fleet and thus ensure the safe operation of the fleet.