A method for preparing an optical film, which comprises applying and developing an application liquid mixture containing a liquid crystal monomer, a chiral agent and a polymerization initiator on an orientation substrate, subjecting the resultant developed layer to a heat treatment, to orient the monomer to a cholesteric structure, and then subjecting the developed layer to a poltmerization treatment, to polymerize the oriented liquid crystal monomer, thereby forming an optical film exhibiting a selective reflection wave length of 100 to 320 nm. An optical film prepared by the above method is reduced in the coloring due to selective reflection.