In this paper a four level model of laser induced collisional energy transfer (LICET) is presented in which the effects of the two intermediate states are considered. The equations of motion for the probability amplitudes of the four states are then obtained. And the analytical expression of the cross section for the LICET transition is derived. The results of numerical calculations in Eu-Sr and Cs-Sr systems show that the conventional three level theory cannot be expected to provide an adequate description of the cross section of the LICET transition if the frequency difference ｜ω21｜ is comparable to the frequency difference ｜ω43｜. But the four-level model can be used to describe the LICET process in all cases.