The invention relates to a closed device for carrying out researches of gas release and gas reforming rule of plants, which mainly consists of a plant growth chamber 1, a gas pipe 2, a gas cooling chamber 3, a liquid header 4, a circulating pump 5, a gas analyzer 6 and an illumination system 7; the closed device is characterized in that growing space of plants is completely closed, and cultivation conditions of illumination, temperature and humidity, wind velocity, water irrigation, and the like, can be properly adjusted and controlled according to experiment needs. The closed device for carrying out researches of gas release and gas reforming rule of plants has the beneficial effects of good tightness, strong external interference resistance, adjustable conditions of illumination, temperature, humidity, wind velocity, water irrigation, and the like, and being beneficial to researches of the gas release and gas reforming rule of plants under the closed condition. The closed device of the invention can be used for the researches of the closed systems such as space stations and space permanent bases, and the like, as well as the plant gas research fields of ground greenhouse and air purification, etc.