Abstract: In order to discuss the importance and influence characteristic of Bezier fitting on welding defect index (DI) and peak-valley index (PVI) in radiographic testing (RT), the characteristic and function of Bezier fitting, definition and computational method of DI and PVI are systematically analysed in this paper. Taking the RT images of industrial weld for example, the comparative computational experiments of DI and PVI under different fitting methods and different defects are carried out. Moreover, the experimental results show that the Bezier fitting method can not only filter the noise and fluctuation skillfully, but also reflect the local distortion caused by the defects accurately,which makes the calculation of DI and PVI more precisely.