Reaction of p—tert—oxocalix [4]arene in cyclohexane at 308nm laser light was investigated by laser photolysis technology at room temperature in research of the reason why p—tert— oxocalix [4]arene was used as polymer stabilizer. Four main absorption were observed at 300nm,340nm,460nm and 540nm. Among them 300nm and 460nm were assigned to the absorption of phenoxy radical and cationic radical respectively. Solvent and pH dependence of cationic radical were investigated. Two—photon process mixed with one — photon process was suggested on the OH bond dissociation. The conclusion was draw that the produce of the relative stable phenoxy radical mediate when p—tert—oxocalix [4]arene was excited is one of the reason.