Abstract: Based on compliance method of the fracture mechanics,the reason of error in the Single Edged Bending (SEB) specimen fracture toughness testing had been researched.The results indicate that the modulus of elasticity is a important parameter to calculate the initialization crack length.The linearity of F-V decision the calculate precision in the test.There have a different between the compliance method and direct reading method.

Key words: fracture toughness, Single Edged Bending (SEB) specimen, compliance, linearity