The invention discloses a method for baking ceramsite by using town sludge, river mud and bentonite. The method comprises the following steps of: milling 30 to 35 weight percent of original sludge, 45 to 50 weight percent of river sludge, and 17 to 23 weight percent of bentonite by wheels, mixing and stirring to homogenize the materials; and aging, pelleting, screening, sintering and expanding, and performing air cooling. The bulk density of the obtained ceramsite is 400 to 500Kg/m<3>, the compression strength is 1 to 3.5Mpa, one-hour water absorption is 8 to 10 percent, and the grain size of the product is 1 to 26mm; and the original sludge, the river sludge and the bentonite are used as the raw materials, the ceramsite is directly baked by taking cavings as fuel, the treatment capacity of the sludge is large, the production cost is low, secondary pollution in the production process is avoided, and the performance of the obtained ceramsite product meets the standard requirement of GB/T17431.1-1998.