The strength will degrade due to the MSD(multiple site damage) in the structure, to avoid the catastrophic failure, the crack growth and reliability of the MSD structure should be evaluation exactly. Considering the lognormal distribution of fracture toughness and stress intensity factor, the multiple-crack propagation reliability model of multiple-Crack structure is developed, including stress strength reliability interference model and second boundary theory. In term of characteristics of MSD cracks growth, two influencing factors having relation with speed of cracks growth are presented. Based on Pairs equation, recursion relation of cracks growth length has been deduced. Combining with the modifiable division of cyclic loading method, the computation work of fatigue crack growth is reduced greatly. Finally, the calculation method of the failure probability for the MSD structure due to the crack propagation is presented. The fatigue life and failure probability of one type MSD crack configuration, which of the collinear fastener holes in rimmed thin panel, is analyzed. Compared with the experiment results, the calculation results show the failure probability of MSD panel is reasonable.