The invention discloses a building formwork flushing device, and relates to the technical field of building formwork cleaning equipment. The device comprises a feeding mechanism, a brushing mechanism,a shaking cleaning mechanism and a discharging mechanism, wherein the feeding mechanism, the brushing mechanism, the shaking cleaning mechanism and the discharging mechanism are sequentially arranged, the shaking cleaning mechanism is composed of a mounting frame, a conveying mechanism, limiting adjusting mechanisms and a shaking mechanism, a gap is formed in the middle of the mounting frame, thetwo limiting adjusting mechanisms are both arranged in the mounting frame, the limiting ends of the two limiting adjusting mechanisms are oppositely arranged, the conveying mechanism is arranged in the mounting frame and located at the bottoms of the two limiting adjusting mechanisms, and the shaking mechanism is arranged at the side end of the conveying mechanism. According to the device, formworks can be shaken and cleaned through the shaking and cleaning mechanism, so that dirt is shaken off, meanwhile, adhered sewage can be shaken off, and reuse is facilitated.