Abstract: The crack tip opening displacement （CTOD） test is conducted to the X80 linepipe steel plate with the-point ending straight notch compact tensile specimen，and the step notch compact tensile specimen. And then according to the calculation as per ISO 12135∶2021，the difference between the CTOD characteristic values of the said two types of specimens are analyzed，and meanwhile the effects on the CTOD characteristic values by the main testing parameters，i. e. the forces F and V_p are preliminarily studied. The results reveal that：the CTOD characteristic values of the three-point bent specimen with side grooves are smaller，whereas the CTOD characteristic values of the three-point bent specimen without side grooves are larger. The influence of Force V_p on the CTOD characteristic value is so much greater than that of Force F. This conclusion provides a certain experimental basis for the different experimental results as generated by the CTOD testing with the three-point-bent specimens with different sample types.