Abstract: In this paper , studies on effects of CO₂ concentration increasing on crop growth ,as well as measuring installation , experimental methods and results in the recent 10 years are summarized. CO₂ enriching enhances crop photosynthesis, reduces transpiration , increases water use efficiency , accelerates growth and development of crop , and enhances dry matter and yield . In general , responses of C₃ crops on CO₂ enhancement are more sensitive than C₄ crops.