The invention discloses a water-based phase change heat expansion type flame-retardant and fireproof coating for tunnels. The raw materials of the coating comprise the following components: expanded perlite supported mannitol-galactose, melamine-phosphoric acid modified lignin, expanded graphite supported chlorinated paraffin, gelatinized starch, light calcined magnesia, magnesium chloride, a polyoxyethylene ether oleate dust preventive, an organic silicon defoamer, hydroxyl silicone oil, amino silicon oil, waterborne polyurethane, nano tin dioxide, titanium dioxide, a filler, aluminum silicate and a polyether-modified polydimethylsiloxane flatting agent. The flame-retardant and fireproof coating absorbs latent heat to resist temperature rise at an initial stage of fire, forms an expandedfoam carbon layer to isolate heat under a high-temperature effect, prevents temperature rise of a tunnel concrete structure, avoids reduction in strength of the tunnel concrete structure, and is thinin coating, high in construction speed, short in maintenance cycle, excellent in water resistance and applicable to a dark and humid environment of the tunnel.