•Investigating the cavitation of jet hydrofoils with different chord length positions.•The mechanism of the influence of the jet on the reflux jet was studied.•Bionic jet can improve the lift-to-drag ratio of hydrofoil.•Hydrodynamic performance and cavitation inhibition are best at the jet position 0.6c.•The return jet on the jet hydrofoil is mainly driven by the clockwise rotation of the bubble. To suppress the cavitation phenomenon of the fluid machinery under high-velocity flow conditions, we designed the shark gill slit jet structure based on the principle of bionics. The selected hydrofoil is an expanding symmetric structure with chord length of 100 mm and span length of 80 mm. a bionic jet with a velocity of 4.836 m/s is placed on the suction surface of the hydrofoil. The jet direction is consistent with the mainstream direction, and numerical simulations are performed for the jet hydrofoil with different chordwise jet positions. The results show that when the chordal jet position is 0.6c, the time-averaged vacuole volume fraction is the smallest, which is reduced by 46% percent compared with the prototype hydrofoil. The lift-to-drag ratio of the jet hydrofoil is improved compared to the prototype hydrofoil. The pressure fluctuations on the suction surface continue to decrease as the longitudinal position of the jet is shifted back, and the shock waves generated by the cavitation collapse of the cloud are continuously suppressed. The return jet on the jet hydrofoil is driven mainly by the clockwise rotational motion of the cavity. Display omitted