Abstract: According to OTC-1 Open top chamber designed by ourselves and experimental data of succssive 3 years,we analysed the effects of CO2 concentration at double levels of natural condition on growth,development and yields of 4 crops based on discussing the physical performance of the equipment.The results showed thatan increasing CO2 concentration accelerated the course of crops growth,increased the height of plant,economical yields and biomass production greatly,and the increasing range of C3 crops was greater than that of C4 crops;The quality of winter wheat and cotton seemly have positive effect,on the contrary,the quality of crn seemly has negative effect,the change of soybean quality wasn't obvious.