Abstract: The fatigue life of civil aircraft structures obeys two-parameter Weibull distribution,its scatter factor is significantly different from that obeys logarithm-normal distribution .To analyze the difference and relation of these two scatter factors,the scatter factor formulas of fatigue life which obeys two-parameter Weibull distribution are presented for theoretical calculation and fatigue testing and the values of scatter factors for different materials are given. Comparison efforts between scatter factors obeying these two distributions are conducted theoretically and numerically. The result provides the important technological approach in determining the fatigue scatter factor of the civil aircraft structures.