Abstract: In recent years, the fracture toughness assessment for small size tubes represented by SG heat transfer tubes has received more and more attention. In this study, a type of radial cracked C-shaped specimen was designed to estimate the fracture toughness of TA16 heat transfer tubes. The expressions of stress intensity factor K and J integral were obtained based on elastic plastic finite element analyses. A group of radial cracked C-shaped specimens for TA16 heat transfer tubes were carried out by using normalization method. The test results show that small data dispersions of J resistance curves and conditional initiation toughness J_Q are observed, the mean value of J_Q is 32.875 MPa•mm, and the standard deviation is 1.377 MPa•mm.