The invention discloses a heating maintenance method for thin-walled concrete of a steel-concrete composite bridge. The method comprises the following steps: spreading and fixing a plurality of carbonfiber heating wires on the upper surface of a steel bridge steel plate; pouring concrete on the upper surface of the steel bridge steel plate, and forming the thin-walled concrete after surface finishing; spreading a moisturizing layer on the thin-walled concrete; spreading a heat-preserving layer on the moisturizing layer; spreading cables on the outer side of the thin-walled concrete; and plugging plugs of the carbon fiber heating wires into plugs of the cables; and enabling the carbon fiber heating wires to work and generate heat. The method uses the carbon fiber heating wires to provide the heat source for maintenance of the concrete, and the carbon fiber heating wires are arranged between the steel bridge steel plate and the thin-walled concrete, so that the maintenance problem of the free surface of the bottom of the thin-walled concrete is well solved.