Hook depth has significant influence on pelagic longline catch performance. This study conducted two-way fluid-structure coupling simulation by using the numerical simulation software ANSYS Workbench 19.2 for tuna pelagic longline which was modeled by Tauti Criterion. In addition, 42 hook depth data measured from tuna pelagic longline operations at 6 survey stations in the high seas near Polynesia Islands (4°S~15°S, 140°W~160°W) in 2016 were compared with the numerical simulation hook depth based on ANSYS Workbench. SPSS t-test was used to analyze the difference between measured hook depth and numerical simulation hook depth. The results show that, the simulated deepest hook depth of pelagic longline is 280~310m, and the hook depth is negatively correlated with velocity. When velocity is low (X=-0.11~0.05 m/s; Y=-0.05~0.03 m/s; Z=0.03~0.11 m/s）, the simulated deepest hook depth is about 310 m. When velocity is high (X=0.28~0.75 m/s; Y=-0.10~0.52 m/s; Z=0.04~0.13 m/s）, the simulated deepest hook depth is about 280 m. There is no significant difference between the simulated and measured hook depth (P=0.241 > 0.05), nor significant difference between the simulated and measured hook depth at each station (P1=0.790, P2=0.337, P3=0.476, P4=0.369, P5=0.175, P6=0.136). The results suggest that the developed longline fishing gear model based on Tauti Criterion and ANSYS Workbench numerical simulation software can be used in the study of longline hook depth.