Recently, the progress in adaptive optics makes the cone effect of Rayleigh laser guide stars be solved fairly. So that the applications of this kind of beacon in adaptive optics, especially in multiconjugate adaptive optics (MCAO) presents a bright future once again. The photon flux density required by the wavefront sensor of MCAO with certain performance is proportional to the number of layers. This results in that the laser energy required by guide stars for "classical" MCAO is very high. In the "new concept" MCAO, however, the Rayleigh beacons are formed by light scattered from whole higher atmosphere but not only a selected thin layer. Then the required laser energy degrades greatly.