Konjac tofu is a traditional Chinese food whose main ingredient is the water-soluble polysaccharide from konjac tubers-konjac glucomannan (KGM). Herein we report an interpenetrating double network polymeric film by crosslinking KGM and polyvinyl alcohol (PVA) with glutaraldehyde under acidic conditions. PVA was introduced into the hydrogel system as a hard skeleton, which not only maintained the biocompatibility of KGM, but also gave the hydrogel superior mechanical properties and solvent resistance. Implanting a colloidal array inside the above film, we obtained a new type of biomass based photonic crystal that is sensitive to a variety of physical and chemical stimulus, especially for methanol. This photonic crystal responds to methanol and methanol vapor, and has the ability to detect methanol in gasoline, which has a good application prospect.