Abstract: In order to popularize the circle hook in Chinese tuna longline fisheries, the mechanical properties of ring hook and circle hook must be understood. The tensile test was conducted by the universal testing machine. The strain and displacement of the ring hook 3.4-4.5 and circle hook 14/0-4.5 during the tensile test were measured by the digital image correlation system. Results showed that:(1) While the tension acted on the circle hook 14/0-4.5 and ring hook 3.4-4.5 was 500N and 800N, the highest strain of circle hook 14/0-4.5 was 0.012 and 0.018, and that of the ring hook 3.4-4.5 was 0.010, and 0.025, respectively;(2) While the tension acted on the circle hook 14/0-4.5 and ring hook 3.4-4.5 was 500N and 800N, the highest displacement of circle hook 14/0-4.5 was 5.16mm and 8.50mm, and that of the ring hook 3.4-4.5 was 4.36mm and 6.01mm, respectively. Results of Chi-square test showed that there were no significant differences in the strain or displacement between circle hook 14/0-4.5 and ring hook 3.4-4.5(P>0.05). Results suggested that the circle hook 14/0-4.5 should be popularized in the Chinese tuna longline fisheries.