Titanium dioxide(TiO2) was used to catalyze the photolysis of benzene, xylene, n-heptane, methanol, acetone, ethylether, formaldehyde, trichloroethylene and perchloroethlene in air. The photolysis was carried out with a high pressure mercury lamp. The degradation rate of these VOCs was more than 80 percent in five minuts except formaldehyde. The effects of catalyst amount, different types of TiO2 catalyst and density of UV on the degradation rate of the VOCs were also studied.