The invention aims at providing a water jet propulsion device of a triangle rotor. The water jet propulsion device comprises a shell, a triangle rotor body, a driving gear and a driven gear. The triangle rotor body is arranged in the shell, the three angles of the triangle rotor body make contact with the inner wall of the shell, the driven gear is arranged in the triangle rotor body and fixed to the triangle rotor body, teeth of the driven gear are located on the inner wall of the driven gear, the driving gear is fixed to a transmission shaft, teeth of the driving gear are located on the outer wall of the driving gear, the driving gear and the driven gear are engaged, a water inlet and a water outlet are formed in one side of the lower end of the shell, a filter is connected with the water inlet, the water outlet is connected with a jet pipe, the jet pipe is fixedly connected with a steering device, and a jet opening is connected with the steering device through a bearing. Water currents can be pressurized in the electric energy-mechanical energy one-time energy conversion process, energy losses are effectively reduced, the propulsion efficiency is improved, and energy output of a main machine is saved.