Abstract: To predict the economical life for pre-corrosion structures, the probabilistic fracture mechanics approach (PFMA) under pre-corrosion environment is presented. The economics and safety of structures are influenced seriously by pre-corrosion fatigue. Based on the principle of PFMA in laboratory environment, the crack growth rule is founded accounting for the pre-corrosion on the ground and corrosion fatigue in the air. While the time to crack initiation (TTCI) is assumed to follow the two-parameter Weibull or logarithmic normal distribution, the equivalent initial flaw size distribution (EIFSD) is back-deduced under pre-corrosion environment. Thusly, the crack size distribution is gained, the damage degree is evaluated and the economical life is predicted. This approach can be applied in evaluating the economical life for pre-corrosion aircraft wing joints successfully.