The invention relates to an efficient molecular energy engine, relating to molecular energy engines and energy sources thereof. The invention needs to solve the problem of increasing the work application efficiency by once under the condition of identical volume of the molecular energy engine. The efficient molecular energy engine has the characteristic that a sub star wheel (5) with the same specification to the original sub star wheel (2) is added to be meshed with a mother star wheel (6), the two sub star wheels are symmetrical in relative to a shaft of the mother star wheel (6), and two movable rotating arms of a rotating shaft (3) are respectively in revolute pair connection with shafts of the two sub star wheels; and one energy source is newly added, one end of the new energy source acts on a shaft of the sub star wheel (5), the other end acts on the arms of the rotating shaft, molecular forces of the two energy sources respectively acting on the two sub star wheels have opposite direction and identical value, and the lines of action are parallel. The power arm of the engine is increased by once, the work application efficiency is increased by once, no waste gas is emitted during the work application of the machine, the environment is protected, no oil, electricity, coal and the like are used during work application, a generator is driven to generate electricity, and the electricity generating cost can be greatly reduced. The engine has great power and extensive purposes and can be used as power of production machines, traffic machines and military machines.