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.