We report rigorous quantum dynamics studies of the Cl+H-2 reaction. The time-dependent wave packet calculations are performed on the semiempirical G3 and the new BW2 potential energy surfaces. Initial state-specific total reaction probabilities and cross sections are calculated and the thermal rate constant is obtained. The quantum dynamics calculations show a striking difference in the energy dependence of reaction probabilities between the G3 and BW2 surfaces, with the former having a smaller reaction threshold. The calculated rate constant on the G3 surface is in good agreement with previous theoretical calculations at room temperature. The calculated rate constant on the new BW2 surface is smaller than that on the G3 surface, and comparison of them with experimental measurement is shown.