Abstract: Based on C8051F005, a new monitoring and controlling system of CO₂ micro-environment for plant tissue culture was developed, which can feed high concentration CO₂ by constant pressure and quantum, and can monitor CO₂ concentration of microenvironment automatically and circularly on line. The developed system resolved such problems as the discharging CO₂ exactly and automatically, the CO₂ detecting precision and stability decreased by high relative humidity in vitro. In the system, the CO₂ concentration in micro-environment can be set up according to demands and be controlled automatically and accurately, and also the decrement of CO₂ concentration and the time length of this course can be recorded. The system can be applied to the research of assimilation rate of CO₂ in different environmental factors, and the large-scale production of plantlets in vitro. By the experiment on Cymbidium hyhridum, holly and Mozzie Buster, the feasibility and reliability of the system have been tested. Results show that this system can meet the control requirement of gaseous environment for large-scale production of plant tissue culture, and can meet the research requirement of building model of micro-environment of tissue culture.