Stable isotopes of CO₂ can reveal much information of photosynthesis and respiration,which contributes to the understanding of the carbon cycle between ecosystem and environment.Here,using the data of CO₂ concentration and its stable isotope measurements,after analyzing δ¹³C and δ¹⁸O,it is found that δ¹³C and δ¹⁸O have the similar temporally and spatially distributive characters.i.e δ¹³C and δ¹⁸O ratioes obviously vary with height,generally,the heavier/lighter isotope ratio is higher at the upper/bottom layer of canopy;and temporally,δ¹³C and δ¹⁸O ratioes are highest from afternoon to sunset,and lower before dawn,with the lowest ratio at the time when air is stable and the CO₂ from the respiration of vegetation and soil reaches the biggest accumulation amount.Finally,by analyzing the relation between δ¹³C,δ¹⁸O and CO₂ using the "Keeling Plot",and discussing the contribution of ecosystem source and sink to δ¹³C and δ¹⁸O,it is found that δ¹³C is mainly affected by the concentration of CO₂,but δ¹⁸O is impacted by many factors,expect the concentration of CO₂,air humidity is also an important factor.