Disclosed is a wide-breadth slurry plate making machine, relating to machinery for producing calcium silicate plates. A breast roll, a beating adjusting device, a small material layer cutting device, a tightener, a carrier roll, a water wiper set, a turning roll, a headbox, a distributor and a water sprayer are installed on a frame; a molding drum is pressed on the breast roll and a blanket is installed on the frame; a scrap conveyer belt is installed beside the breast roll which is connected with a main driving shaft; and the molding drum is has a transverse breadth. When in work, the material slurry is dragged out by the moving blanket and is brushed to be flat and even by a brush roll; the breast roll drives the blanket to move; the material slurry on the blanket is dehydrated by the water wiper set and a high-pressure vacuum box and then is cut by the small material layer cutting device; the dehydrated small material layer is wound on the molding drum, and when reaching certain thickness, the small material layer is cut and then is put on a blank receiver, forming a plate blank. The length of the molding drum is increased by nearly one time as compared with the old molding drum, and the longitudinal single breadth can be changed to be double breadths, thereby realizing producing four calcium silicate plates on one production line at one time. The wide-breadth slurry plate making machine is high in production efficiency, less in investment and small in energy consumption.