The influence of the etalon effect on the laser output of the uncoated alkali vapor cell windows on the inner surface is experimentally studied. The research results show that the two inner surfaces have different spot patterns when they are used as the laser output surface, and both of the cases are accompanied by parasitic spots. The parasitic spots are caused by the wedge angle of the two windows of alkali vapor cell. The experimental and theoretical results of the threshold at different output coupling rates are compared. It is verified that the uncoated inner surface of the alkali vapor cell has etalon effect and multiple reflections. When the alkali cell replaces output coupling mirror, the etalon effect is the main factor of the laser output. In this case, the rubidium laser of 1.8 W is obtained, whose optical efficiency is 10.2% and slope efficiency is 15.8%.