Abstract: The conventional load-strength interference model is suitable for the static reliability analysis of a component, where the load is independent of strength. With the strength degradation taken into account, the residual strength of a component is the function of the magnitude and frequency of loading. The conventional load-strength interference model is therefore unable to analyze the reliability of a component or system if the strength is in degradation. By defining the equivalent coefficient of the loading frequency and referential load, a load-strength interference model considering the correlation between the load and the strength is developed, which can be used to evaluate the reliability of a component or system in strength degradation under random load. In addition, the common cause failure due to sharing the same random load affects greatly the reliability analysis of a system. A reliability model is developed for the system considering the common cause failure is derived. A numerical example is given to show the rationality and effectivity of the reliability model.