The invention provides a dolphin-imitating marine propulsion device and belongs to the field of ships. The dolphin-imitating marine propulsion device comprises a motor having a function of providing power, a hydrofoil, connecting rods, a triangular connecting rod, rockers, pins, gears, a supporting frame and a hinged support. According to the dolphin-imitating marine propulsion device, the motor is used for driving the gears to move, the gears drive the connecting rods to move through the pins, the two connecting rods are used for driving one rocker and the triangular connecting rod to move correspondingly, and the triangular connecting rod drives the other rocker to move. The hydrofoil can generate the movement effect of vertical fluttering like the tail of a dolphin under the driving of the combination of the two rockers, and therefore propulsion can be generated.