Abstract: With reference to the principle of crack length measurment with compliance method,interferential factors in elastic modulus measurement of metal materials with three-point bend specimen were investigated.On the basis of above investigation,fatigue crack length of bigger three-point specimen for CTOD test with compliance method were preformed.Fracture measurement manifested that base metal specimen and weld specimen have similar original crack length in compliance method measurement.So the measure accuracy for further CTOD test is ensured.