Lightweight gypsum plaster mortar

The invention belongs to building mortar, and particularly relates to lightweight gypsum plaster mortar which is the secondary development of gypsum plastered product technology. The lightweight gypsum plaster mortar is used for leveling inner sides of outer walls, inner partition walls and ceilings of buildings, and the heat-insulated effect is good. Because the flue gas desulphurized building gypsum of power plants is used, the problem of disposing and using the desulphurized gypsum is solved, and the circulating economy is developed. The method for preparing the plaster mortar comprises the following steps of: accurately weighing up the following materials in part by weight: 70 to 80 parts of flue gas desulphurized gypsum of power plants, 15 to 25 parts of vitreous hollow microsphere, 0.2 to 0.4 part of cellulose ether, 0.3 to 0.6 part of air entraining agent and 0.2 to 0.5 part of retarding agent; and putting the materials into a container, adding 60 to 120 parts of water into the container, and uniformly stirring the mixture at the normal temperature to obtain the lightweight gypsum plaster mortar. The lightweight gypsum plaster mortar has the advantages of moderate strength, unnecessary additional making of protective covering, direct leveling after plastering, high performance cost, high workability, short construction period, functions of preventing fire, absorbing sound, and adjusting air humidity and no emission of CO2 in the production process.