In order to study the effect of jet hole structure parameters on underwater jet drag reduction， this paper establishes a bionic fish model with tuna as the bionic object， and adds jet holes to the side of the bionic fish model by simulating shark gills. The effects of the velocity of the main stream field， the shape， height， position and aspect ratio of the jet hole on the surface drag reduction of the bionic fish are analyzed by numerical simulation. The response surface multi-objective parameter optimization is carried out on the structural parameters of the jet hole through Design-expert software， and the influence of the structural parameters of different jet holes on the surface drag reduction of the bionic fish is further analyzed. Finally， it is determined that the shape of the back triangle is added at the distance of 5 mm from the head of the fish， and the height is 6 mm. The ideal drag reduction effect can be achieved when the jet hole with the aspect ratio of 4 is used. In this case， the total resistance of the model is 2.510 21 N， and the corresponding drag reduction rate is 6.49%. Through in-depth analysis of the influence of jet hole structure parameters， this paper provides an important theoretical basis and experimental guidance for underwater jet drag reduction technology， and expands a new possibility for the application of bionic technology in the field of underwater fluid mechanics.