多部位损伤(MSD)会使结构的强度大幅降低，为了防止由此造成的灾难性破坏，必须对 MSD 结构在整个寿命周期内的裂纹扩展情况及可靠性水平进行准确评估． 文中在假设 MSD 结构断裂韧性和应力强度因子服从对数正态分布的基础上，结合应力强度干涉模型和二阶窄边界理论，建立了 MSD 结构的裂纹扩展可靠性模型;考虑 MSD 结构多裂纹扩展过程中的两类影响因素，推导了疲劳载荷作用下的裂纹扩展增量递推公式;结合变载荷间隔分段处理方法，提出了 MSD 结构随载荷循环次数变化的失效概率计算方法． 通过对一受远场均匀载荷作用的含共线孔边裂纹的 MSD 壁板结构的分析计算，得到了 MSD壁板结构失效概率随疲劳载荷作用次数的变化趋势，并将其与试验值进行比较，较为准确地反映了 MSD 壁板的失效趋势．

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.