The invention discloses a template supporting structure for a cast-in-situ limestone flour chamber. The template supporting structure comprises an inner template supported along the circumference direction on one side of a double-layer reinforcing steel bar rack, an outer template supported along the circumference direction on the other side of the double-layer reinforcing steel bar rack, a reinforcing steel bar inner support and a reinforcing steel tube. The inner template and the outer template are combined steel templates; a deformation adjusting groove is arranged on the back face of a panel; a deformation adjusting opening is formed between an edge rib and a vertical rib on the deformation adjusting groove; a plurality of reinforcing loops are uniformly distributed in the vertical direction on the outer side of the inner template; a plurality of reinforcing belts are uniformly distributed in the vertical direction on the outer side of the outer template; the reinforcing steel tube is arranged at the upper ends of the inner template and the outer template; buckles are fixedly mounted at the both ends of the reinforcing steel tube; and the buckles are respectively clamped on the outer sides of the inner template and the outer template. The invention provides the template supporting structure for the cast-in-situ limestone flour chamber. The inner template and the outer template of the limestone flour chamber are supported by using the template supporting structure, so that the supporting density of a scaffold can be greatly reduced; the labor and the material can be saved; and the phenomenon of template extension in a casting process can be prevented simultaneously. Therefore, the casted limestone flour chamber is formed in a good shape.