The pulse profile influence of excitation light on the two-photon absorption coefficient \beta is theoretically and numerically studied. Based on Gaussian spatial and temporal laser, we obtain an expansion formula of energy transmission. As compared with a plain beam and a pulse beam that is rectangular in time but Gaussian in space, the relative deviations of \beta turn out to be about 214% and 47%, respectively. These differences indicate that a smaller \beta may be obtained than the real one in usual nonlinear transmission. Our result suggests that by taking real pulse profile into account, a more exact \beta can be derived in energy transmission measurement.