Powder special for mechanized construction plastering mortar

The invention discloses a powder special for mechanized construction plastering mortar, which is formed by mixing portland cement clinker, plaster, granulated blast-furnace slag, coal ash, limestone powder and a chemical addition agent, and a mass ratio of the portland cement clinker to the plaster to the granulated blast-furnace slag to the coal ash to the limestone powder to the chemical addition agent is (100-300): (50-100): (50-200): (100-400): (100-400): (2-5). A scientific proportioning relation is utilized by the invention, so that the prepared building plastering mortar have an excellent water-retaining property, a thickening property, a mechanical transport property and sag resistance on the wall, and meanwhile, the binding power of the hardening mortar and the matrix is improved, the size shrinkage rate is reduced, and the trends of powder falling, hollowing and cracking are reduced.