Objective In order to indicate the change of the carbon dioxide content in food packaging more conveniently, a kind of carbon dioxide indicator was studied in this paper. Methods The paper used pH-sensitive indicators as materials and took the estimation method of pH in CO2-H2O system as the theoretical basis to study carbon dioxide indicator. And the colorimetric system of the indicator color based on Lab color space was also used in the paper. Results By means of measuring pH of carbon acid solution under different CO2 concentrations and using the mathematical analysis software to simulate functional relation between CO2 concentrations and pH of carbon acid solution, a high correlation model of carbon dioxide content and pH value was derived by model fitting. Based on the model and overall consideration factors such as the quantity of color gradation and color change degree, we got an indicator formula∶methyl red： bromothymol blue=3 ∶ 2 and the concentration was 5%. Combining the significance analysis of chromatic aberration, sensory evaluation and the color simulation, we found that the indicator could produce obvious color changes in the carbon dioxide concentrations of 0, 5%, 7%, 13%, 18%, 34%, 43%, 61% and 78%. Conclusion The solution composed of 3/5 methyl red and 2/5 bromothymol blue could be used as a carbon dioxide indicator and the mass concentration of the indicator solution was 5%.