The atomic and molecular reaction dynamics for T+OD have been studied basad on the potential energy function of DTO(1 A1) by Monte Carlo quasi-classical trajectory approach. It is shown that the reaction T+ODDTO with a long-lived complex has a threshold energy at low collision energy, which accords with the potential curve. The interchange reaction increases with collision energy increasing, until the DTO molecules decompose into D, T, and O completely, and these reactions have threshold energyies too. The trajectories and the collision cross-sections of T+OD(0, 0) and D+OT(0, 0) are different due to the isotopic effect of D atom and T atom.