The reactive and nonreactive inelastic probabilities are calculated for the collisional deexcitation of vibrationally excited HCl (v = 1, 2, 3) molecules by Cl atoms using collinear exact quantum method. The results indicate that the reactive and nonreactive inelastic probabilities oscillate with energy; according to the probability of channels of the reaction and nonreaction it is expected that both reactive and nonreactive inelastic collisions are all equally effective in the deexcitation of HCl (v = 1, 2, 3) by Cl atoms, which is good agreement with the results obtained by Wilkins; the probability has a close relation with the quantum number v of the vibrational states of the HCl, we found P(vv') almost-equal-to 10(v+v'-2(v"+1))P(vv"), (v > v' > v"). This is in good accord with Moor's experimental results.