The mechanism is studied of energy transfer from heavy ions to D atoms which then induce D-D fusion reaction. The Proton yield has been measured from the TiD target in the D（d

p） T reaction induced by 197An bombardmeat in the energy range from 1.0MeV to 5.2MeV.The results can be explained by a two step cascade collision model

which indicates that the energy transfer is carried out by elastic collisions between D atoms and hem ions.