Abstract: Two series of fatigue crack growth rate (FCGR) tests using three-point bend specimen with different integral knife-edge designs are performed. Effect of elastic modulus on the measurement of fatigue crack length using compliance technique is analyzed.The results show that both positive and negative deviation of the elastic modulus from real value in the measurement with compliance technique will influence the accuracy of lg(d a /d N)-lgΔ K curve providing an experiment back for selecting the type of integral knife-edge of the three-point bend specimen in FCGR test.