Abstract: Based on the results of the determination of the relative quantum yields and the content of ¹O₂ products of α and β-pinene and 1,4-diphenyl-1,3-butadiene in a series of solvents and the analysis of the kinetics of the reaction of β-pinene,the solvent effects were discussed. Solvent polarity,solvent viscosity give the identical influence upon both DCA-sensitized (photooxygenation and the fluorescence quenching rate constants of DCA. For weak electron donors,α and β-pinene,the relative quantum yields (φ_r) of their photooxygenation which are the same as their k_q values depend obviously on solvent polarity. And also similar to kq values,the main factor which influences φ_r for strong electron donor,1,4-diphenyl-1,3-butadiene,is the solvent viscosity. It may be concluded that electron transfer mechanism is operating in DCA-sensitized photooxygenation including ¹O₂ products formation.