The photochemical and photophysical behaviors of tri(4-tert-butoxycarbonyl oxyphenyl) sulphonium salts have been investigated. In argon-satureted acetonitrile, the quantum yields of Bronsted acid formed during photolysis of these compounds was abount 0.5. In the transient absorption spectrum excited by 266nm in mathanol and dioxane an evident absorption peak at 360 nm decayed in accordance with pseudo-first-order reac tion was observed. In the presence of poly-p-hydroxystyrene or diphenyl sulphide, the apparent second-order reaction decay rate constants were 107 and 108 L·mol-1 ’s-1 t re spectively. Results indicated that the transient absorption peak at 360nm was attributed to the diphenyl sulphide radicaJ cations formed in photolysis of sulphonium salts, which were proposed by abstraction of hydrogen from solvent or polymer to yield the protonic acid and diphenyl sulphide as listed in eqns. (1) and (2). The influence of non-nucleophilic anions of title compounds on their photochemical behavior was just less important. The photochemical and photophysical behaviors of tri (4-tert-butoxycarbonyl oxyphenyl) sulphonium salts have been investigated. In argon-satureted acetonitrile, the quantum yields of Bronsted acid formed during photolysis of these compounds was abount 0.5. 266 nm in mathanol and dioxane an evident absorption peak at 360 nm decayed in accordance with pseudo-first-order reac tion was observed. In the presence of poly-p-hydroxystyrene or diphenyl sulphide, the apparent second-order reaction decay rate constants were 107 Results showed that the transient absorption peak at 360 nm was attributed to the diphenyl sulphide radica J cations formed in photolysis of sulphonium salts, which were proposed by abstraction of hydrogen from solvent or polymer to yield the protonic acid and diphenyl sulphide as listed in eqns. (1) and (2). The influence of non-nucleophilic anions of title compounds on their photochemic al behavior was just less important.