The decomposition of gaseous trichloroethylene by UV/TiO2 process in an annular photoreactor fixed with TiO2-coated nonwoven fiber textile was studied under various UV light intensities, humidities, oxygen contents and retention times of carrier gases. Experimental results indicated that the photocatalysis by UV/TiO2 process is technically feasible to decompose trichloroethylene in air streams. A design equation combining the equations of continuity and surface catalytic kinetics was developed for describing the decomposition of trichloroethylene in air streams by UV/TiO2 process at various operating conditions.