The accelerating effect of oxygen in the benzophenone／triethylamine／oxygen (BP/TEA／O2) system was studied．It is necessary to keep high concentration ratio of TEA／O2 in order to achieve the accelerating eftect．Experimental results indicated that oxygen in the system through photooxygenation reaction transformed to peroxides．The rate of oxygenation depended on[BP] and [TEA]0.8 Subsequent photosensitized de-eomposotion of peroxides led to an increase in forming primary radioals．Ftom the determintd Kp／Kt1/2 value it may be interpreted as the evidence of the primary radical termination．The kinetic orders related to Dhotooxidation of oxygen have been deter-mined and the corresponding reaction mechanisms are also discussed．