The aim is to identify and indicate the acidic gas (CO2 for example) generated during the process of food freshness decline. High amyloid-based pH responsive food packaging materials (HASF for short) prepared by the method of polymer solution polymerization are made from high amylose corn starch, polyvinyl alcohol, crosslinking agent and other auxiliaries and pH responsive composite indicators. The light transmittance, water absorption, water solubility and mechanical properties of the HASF indicator material are analyzed to determine the optimal ratio. Through the identification and detection of CO2 by the indicator materials, the volume ratio of methyl red to bromothymol blue in the composite indicator is determined to be 1 : 2 and the optimal additive amount is 6%.The infrared spectrum and scanning electron microscope show that the internal compatibility of the components is good. Therefore, the performance of the food packaging composite film is stable. The indicator materials can be used for food packaging materials. At the same time, the indicator materials can identify and indicate acid gas through color change, which provides the possibility for the intelligence of food packaging materials.