The photooxidation damage of Lysozyme induced by duroquinone was studied by lysozyme activity analysis and sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). It is suggested that the mechanisms and products of oxidative damage were relative to the concentration of duroquinone, the time of irradiation and the ambience. The type I process was considered in nitrogen saturated solution, whereas both type I and type II were involved in under aerobic atmosphere and type II was the dominant process. The study also indicates that antioxidants such as hydroxycinnamic acid derivatives can reduce the damage of lysozyme effectively.