The invention relates to an energy-saving device for preventing a six-stroke V9 engine from idling and flaming out, and belongs to the technical field of power machinery. The energy-saving device comprises a balance weight and an output shaft of the six-stroke V9 engine. Nine cylinders are arranged in two banks, and the two banks of cylinders form a 60-degree included angle. The output shaft rotates by 360 degrees to form six periods of torque pulsation. The part, between the six-stroke V9 engine and a flywheel, of the output shaft is provided with a combined permanent magnetic unit for enhancing inverse torque pulsation. The combined permanent magnetic unit comprises a rotary permanent magnet assembly fixed to the output shaft of the engine and a fixed permanent magnet assembly fixed to a rack and matched with rotation permanent magnets. The rotary permanent magnet assembly is composed of the twelve permanent magnets which are alternately arranged along the circumference and are identical in size and opposite in polarity. The fixed permanent magnet assembly is composed of twelve permanent magnets which are alternately arranged along the circumference and are identical in size and opposite in polarity. Magnetic lines of force penetrate through air gaps between the rotary permanent magnet assembly and the fixed permanent magnet assembly to generate permanent magnetic torque pulsation.