Abstract: In accordance with the BS7448,CTOD(crack tip opening displacement) tests were conducted at-15℃ for welded joints of X65 pipeline steel.The three-dimensional finite element numerical simulation was performed on the CTOD specimen.According to the requirements of the standard,the specimen was a standard three point bending shape.Then the CTOD test were performe,and the results were calculated using the p-V curves Finally,The test results were generalized and analysed.Especially,the observation of a slice containing the fracture face explained the dispersity of the test values,and validated the test results.From the results of the finite element analysis,the simulated p-V curve was obtained.It could be seen that the simulated curve was within the experimental curves,so the numerical simulation was accurate.All the above indicate that it is a practical method to calculate CTOD fracture toughness by finite element numerical simulation when no other methods are available.