Abstract: The enhancement effect of translational energy of incident molecules on the laser induced gas-surface reactions is studied using a CW supersonic molecular beam technique coupled with time-resolved mass spectrometry. For the visible (560 nm) lasre induced etching reactions of Cl_2 with Ge(111), Si(111) and GaAs(100) surfaces the reaction yields increase obviously with increasing translational energy of incident Cl_2 molecules. There appears to be a translational energy threshold which has a value of 5—7 kJ·mol~(-1) for different etching reactions. Moreover, the dependence of the translational temperatures of the desorbed reaction products on incident translational energy of Cl_2 molecules is investigated by the measured TOF spectra of the products. The results can be explained by the promotion of dissociative chemisorption Cl_2 molecules on semiconductor surface with raising of the incident Cl_2 translational energy.