Vibration mixing and vibration mapping, which we proposed recently as novel methods to describe vibrational interaction in terms of normal modes, were applied for the prediction and understanding of the transition normal vibration (TNV) in atom + molecule type reactions (H.+H-H -->, H.+H2C=CH2 -->, and H- + oxirane -->). According to the equations of vibration mixing, we derived vibration mixing rules for the prediction of the TNV which consist of a principle for the selection of the candidate normal modes growing into the TNV and of the estimation of the sign and magnitude of the mixing coefficients for the normal modes to mix in. Thus, the possible TNVs can be predicted by pictorial examination of the normal modes of the reactants. The results are in good agreement with those of vibration mapping.