The invention discloses a tunnel water vapor humidity simulation device, a tunnel environment quantitative simulation system and a method. The tunnel water vapor humidity simulation device comprises a water storage part, a moving mechanism and a water vapor ejector; the water storage part is used for storing water sources; the moving mechanism is arranged at the bottom of the water storage part to drive the water storage part to move; the water vapor ejector comprises an ejector spray head which is used for spraying water vapor into a tunnel simulation device and connected with the water storage part through water flow pressurizing equipment; by simulating the true water vapor environment characteristics of a tunnel, the sensitivity of test equipment on the water vapor concentration can be conveniently acquired indoors, then accessory type selecting and relevant parameter adjusting of tunnel structural surface collecting equipment are guided, and the reliability and the practicability of research and development equipment are improved. Accordingly, the structure is simple, operation is convenient, the working efficiency is improved, the construction time of occupying the actual tunnel site is omitted, and financial and material resources in the tunnel construction process are saved.