Abstract: On the basis of Impulsive Collision Model, the product rotational alignments of reactions A+BC→AB+C have been studied. The alignment corresponding to the relative velocity of the reactants,i、e.—＜P_z（Ĵ∙\hat J\rm\cdot\hat k）＞, deponds only on the ratio of the momenta of A and B after the repulsive energy R released.—＜P_z（Ĵ∙\hat J\rm\cdot\hat k）＞increases with the increase of the ratio. Consequently with increasing the repulsive energy R and the mass of Catom, — ＜P_z（Ĵ∙\hat J\rm\cdot\hat k）＞is decreased. The modeling calculations are in good agreement with the experimental results.