The invention relates to a natural gas engine structure for mixed double-injection of cylinder outer cold water and in-cylinder hot water. The natural gas engine structure comprises a natural gas engine body, an air inlet manifold, an exhaust manifold, a natural gas injector, a spark plug, an in-cylinder water sprayer, a high-pressure water pump unit, a cylinder outer water sprayer, a low-pressurewater pump unit, a heat exchanger and a electronic controller; and the in-cylinder water sprayer is arranged in the natural gas engine body, the high-pressure water pump unit communicates with the in-cylinder water sprayer, the cylinder outer water sprayer is arranged in the air inlet manifold, the low-pressure water pump unit communicates with the cylinder outer water sprayer and the electroniccontroller is electrically connected with the natural gas injector, the spark plug, the in-cylinder water sprayer, the high-pressure water pump unit, the cylinder outer water sprayer and the low-pressure water pump unit. Compared with the prior art, the natural gas engine structure has the advantages that hot water sprayed in a cylinder is used for rapidly vaporizing to absorb heat, so that the temperature in the part, close to a combustion top dead center, of the cylinder is reduced, and the generation of knocking is inhibited; meanwhile, the heat for heating the water comes from recovering tail gas energy by a exchanger, so that the working medium in the combustion process is increased, the heat loss is reduced, and the heat efficiency of the natural gas engine is improved.