The invention discloses a putty powder mixing device for a building. The putty powder mixing device comprises a stirring barrel and a base, the base is arranged at the bottom of the stirring barrel, acover is arranged at the top of the stirring barrel, the cover and the stirring barrel are fixed through threads, tempered glass is arranged on the surface of the cover, the tempered glass is embedded in the surface of the cover, and a feeding port is formed in the top of the cover. The feeding port and the cover are fixed through a buckle, a through hole is formed in the middle of the tempered glass, an electric drill is arranged in the through hole, the electric drill and the through hole are fixed in an inserted mode, a sleeve rod is arranged at the output end of the electric drill, a threaded rod is arranged at one end of the sleeve rod, and the threaded rod and the sleeve rod are fixed through threads. Through the arranged base, space is provided for discharging, convenience is improved, through the arranged electric drill, rotation of the stirring blades is achieved, the working efficiency is improved, through the arranged tempered glass, the real-time monitoring function in thestirring barrel is achieved, safety is improved, through the arranged feeding port, needed materials are put in, and convenience is improved.