Abstract: For the diffusion defects pipeline with HIC micro-cracks, growth rules of micro-crack, crack growth rate and influence factors of crack growth are researched.Growth process of micro-crack of damaged pipeline is simulated using finite element method of ANSYS software.Results show that for the pipeline with diffusion defects, corrosion at internal wall of pipe is most serious, and corroding along the internal wall of pipe to external is gradually weakened.Carrying out finite element analysis about diffusion micro-crack growth for corroded pipeline can provide a technical support in residual strength and se rvice life evaluation of corroded pipelines.