The invention discloses a miniature underwater thruster.The miniature underwater thruster comprises a shell, a propeller shaft, propellers, a speed reducer, a motor, a magnetic coupler, a pressure pipe, a shell connecting sleeve, a propeller shaft sleeve, a sacrificial anode and a motor heat dissipation frame, a cabin formed by the shell in an enclosing mode is internally provided with the motor, the speed reducer and the magnetic coupler in sequence, one end of the magnetic coupler is connected with the output end of the speed reducer, the other end of the magnetic coupler is connected with the propeller shaft, the propellers are arranged on the propeller shaft and fixed through the sacrificial anode, the rear end of the shell is connected with the pressure pipe through a pressure pipe fixing sleeve, the shell is connected with the propeller shaft sleeve, and a magnetic separation head is arranged on the joint.The miniature underwater thruster has the advantages that the structure is compact and reasonable, the volume of the thruster is reduced, the power loss is reduced, the motor heat dissipation problem is effectively resolved, the motor can run for a long time in a super-power mode, the pressure pipe is adopted to serve as an underwater channel of an electric wire, and the problem that the underwater thruster energy and control signal transmission is inconvenient is solved.