Abstract: The Kinetic equation of energy transfer in the entire concentration range for γ-irra-diated n-C12H26-TBP system was obtained by subdivided approximate method, that isHere GA is the number of DBP-MBP molecules formed per 100 eV of energy absorbed by TBP after sensitization in the system, GA0 that of pure TBP, and α the content ofcertain excited state of TBP. It is determined that0.91 1/mol. Theoretical curve agrees well with the experimental results.Kinetic study shows that bimolecular collision mechanism predominates in the process, of energy transfer, especially at TBP<0.3 mol/1. If it is controlled by diffusion, then the energy transfer rate constant k6~1010 1/mol sec and the life time of certain excited state of n-C12H16 is about 10-9 sec. Obviously, when TBP>0.3 mol/1, other energy transfer mechanisms take place.