In this paper, the Gaussian, Lorentz and Lorentz-Gaussian beams are used as the pump beam in a diode side pumped Nd:YAG leaser and the effects of these beams on the absorption efficiency of the laser are investigated. It is illustrated that the absorption efficiency for Lorentz-Gaussian profile is higher than the two others. Also has been shown that for entrance Lorentz-Gaussian profile, the absorption efficiency is increasing with decreasing the distance from the diodes to the slits and increasing the diameter of the laser rod. It is shown that there is an optimum slit width corresponding to the maximum absorption efficiency for any laser diode side-pumped solid-state lasers.