Abstract: Photochemical reaction of 2,4,6-tri-t-butyl-4-methoxy-2,5-cyclohexadienone in the solid-state has been investigated.Photoketone,photophenol,lumiketone were obtained.The ratios of products varied with temperature.In solution,the ratio was not effected by temperature.Irradiation of crystals of 2,4,6-tri-t-butyl-4-methoxy-2,5-cyclohexadienone with filter of solution of NaNO₂,the lumiketone was obtained almost quantitative yield.If the mixture of lumiketone containing a small amount of naphthalene is irradiated,the ratios of products varied with amount of naphthalene.