The bright laser sodium beacons are beneficial to enhance the accuracy and sensitivity of wavefront sensing. But the recoil and downpumping limit the increase of the excited state probability and decrease the sodium spontaneous radiation rate and the number of return photons in the process of laser interacting with sodium atoms. By investigating on the recoil and downpumping effects which the narrow band and broad band lasers act on sodium atoms in mesosphere, the conclusions show that the effects of recoil and downpumping of the narrow band laser are more severe than the ones of the broad band laser, but the spontaneous radiation rate is faster than that of the broad band laser and the number of return photons is distinctly more than the one excited by the broad band laser, when the low energy continuous wave laser interacts with the sodium layer in the mesosphere. However, the broad band laser has the easily unsaturated merit and the less recoil effcts.