Abstract: Understanding the hook depth of longline fishing gear is crucial for improving the catch rate of target species and reducing the bycatch. Based on the tuna longline survey data collected in the high seas west of Polynesia from January to August of 2016, we employed the finite element method to construct a three-dimensional dynamic model. We used the explicit sixth-order five-stage Runge-Kutta method to calculate hook depths, and utilized a numerical model with temperature-depth recorder (TDR) mass in water was to correct the simulated depths without TDR mass in water. Then we conducted a one-way ANOVA to compare the hook depths obtained from numerical models with and without TDR (2050) mass in water, against the actual TDR measurements and corrected depths at sea. The results show that: 1) There was no significant difference between the hook depth calculated by the numerical models of mass in water with and without TDR and the hook depth measured and corrected by TDR at sea (p>0.05), indicating that the numerical model was correct. 2) As the current weakened, the influence of TDR on the depth of settlement increased gradually. 3) When the flow velocity was less than 0.16 m·s⁻¹, the influence of TDR on the depth of the hooks in the shallow, middle, and deepest groups of longline fishing increased by an average of 1.0, 2.3, and 3.7 m, with correction factors of 1.010, 1.011, and 1.016 for each group, respectively. 4) The TDR (2050) from the Canadian RBR Company can be effectively utilized for measuring the depth of longline fishing hooks, and its impact on the depth of the hook can be disregarded in the future. The dynamic model of longline fishing gear established in this study can simulate the sinking depth of the hook under the action of three-dimensional currents, explore the influence of TDR mass in water on the sinking depth of longline fishing, and perform the three-dimensional visualization of spatial shape changes.