An infrared sensitive and chemical treatment free photosensitive composition, includes, based on weight percentage, 30-70% of a water soluble thermally cross-linking resin, 1-20% of a water-soluble photocross-linking polymerized resin, 10-50% of a photopolymerizable oligomer, 1-30% of a multifunctional monomer, 1-20% of a cationic photopolymerization initiator, and 1-20% of an infrared irradiation absorption dye. The photosensitive composition of the present invention is useful for preparation of an infrared sensitive and chemical treatment free lithographic plate. The lithographic plate of the present invention has a high sensitivity and a good mesh point reduction, and after exposure to an infrared light source, can be printed directly after being washed with tapped water or without any washing and processing step, and has a long run length.