According to standard test method for J - integral characterization of fracture toughness-ASTM standards: E 1152-87, E813-89, CEGB Report R/H/R5-Rev . 3 (1986) Appendix 1 and GB2038 - 91 of China etc, , for several steels (17MnR, 15MnVNR, CF62) and their welding zones of home manufacture using in pressure vessels JIC and JR curves have been measured and determined in this paper. By test result, JIC and JK curve of every one are compared and analysed. Finally, the method for determining the fracture toughnes...