Conducting finite element simulation modeling for the tightening process of four sizes of flared tube fittings. Develop a model for assessing the sealing performance of flared tube fittings, Through analysis of the plastic deformation, contact pressure, and changes in the length of the sealing line formed by the flared tube fitting and the tube fitting, the sealing performance during the tightening process of four sizes of flared tube fittings can be evaluated. Optimal tube pretension parameters can be extracted during the time when the sealing performance is best, and by utilizing the torque-twist relationship, the optimal torque values for flared tube fittings with diameters of φ8 mm, φ12 mm, φ20 mm, and φ30 mm can be determined to be 26 N·m, 35 N·m, 175 N·m, and 238 N·m, respectively. To conduct the tightening leakage test for the corresponding specification flared tube fittings, determine the experienced torque parameters for the four specifications of the tubes as follows: 25 N·m, 30 N·m, 150 N·m, and 210 N·m. Comparing the simulated and experimental torque values for the flared tube fittings of the respective specifications, the relative errors are respectively 3.8%, 14.3%, 14.3%, and 11.8%. Conduct another leakage test after tightening the tubes according to the simulation results, without any leakage phenomenon occurring, further verifying the reliability of the simulation model, providing a certain theoretical basis for efficient force determination of flared tube fittings.