As commonly recognized, global warming is mainly caused by the emission of carbon dioxide (CO2). Stomatal conductance (gs) plays an important role between the vegetation and atmosphere water and carbon exchanges, and therefore it is also a key model parameter in the water and carbon models. Accompanying with the elevated CO2 concentration, the response of stomatal conductance, correlating with transpiration and photosynthetic capacity, to elevated CO2 concentration is open to question. Stomatal conductance as an important index shows sensitive responses to elevated CO2 concentration, i.e., stomatal conductance decreases with elevated CO2 concentration and maintains lower intercellular CO2 pressure by 20% 30% than atmosphere CO2 concentration. We elucidated current understanding of the mechanisms that underlay the response of stomatal conductance to variable CO2 concentration, and an model that described the response of stomatal conductance to variable CO2 concentration was derived based on the physiological and biochemical mechanism of stomatal movement. By using Li-6400 portable photosynthesis system, stomatal conductance at leaf level was measured under controlled photosynthetic photons flux density (PPFD) and variable CO2 concentration conditions across 9 plant species, including crops such as maize (Zea mays), soybean (Glycine max), rice (Oryza sativa) in Northeast China, and woody plants such as slash pine (Pinus elliottii), Banana Shrub (Michelia figo), Orange (Citrus) in Southeast China and herbaceous plants such as Leymus chinensis, Agropyron mongolicum and Stipa grandis in Northwest China. Meanwhile, the model was verified using the dataset of 9 plant species at leaf level and at short-term. Both the observation and model results showed that the stomatal conductance gradually reduced with the increase of CO2 concentration, but this increasing trend would decrease with the gradually increase of CO2 concentration. The model could be expressed by gs=gmax/(1+Cs/Cs0), where gs is the stomatal conductance, Cs is the CO2 concentration, gmax is the maximum stomatal conductance, and Cs0 is the experimental constant. The model also showed that the responses of stomatal conductance to variable CO2 concentration were hyperbolic. The parameters, gmax and Cs0, were provided for the 9 plant species. This model could simulate the response of stomatal conductance to variable CO2 concentration well, with the specific physiological meaning of the model parameters. However, the impact of the model under elevated CO2 concentration should further be investigated on the water and carbon exchanges. The model only accounted for the variable CO2 concentration, and not for other different environmental factors. Compared with the Javis and Ball-Berry stomatal conductance models, breakthroughs in this model should be achieved in the response of the coupling different environmental factors in future. Furthermore, this model was only verified under the changing CO2 concentration in short-term, but the adaptability of this model under long-term of elevated CO2 concentration should also be confirmed.