The invention discloses a chemical solution injection electro-osmosis combined gravel pile composite foundation method. The method comprises the following steps of: driving a gravel pile into a soft soil foundation, inserting a metal electrode into the gravel pile, injecting chemical solution, and then supplying direct current, wherein under the action of the direct current electric field, the water with positive charges and cationic solution flow to the cathode and the anionic solution with negative charges flows to the anode so as to form electro-osmosis and chemical reaction, the water in the soft soil is drained from the top of the gravel pile, the consolidation of the soil is accelerated, the strength of the soil is improved, and the sediment produced by the chemical reaction plays acertain role in cementing on the gravel pile and the soil; laying a mattress layer at the top of the pile to form a composite foundation; and meanwhile, arranging a vertical enhancing body and chemical electro-osmosis soil in the soil, and coordinating the pile-soil rigidity ratio so as to economically and effectively improve the treatment strength of the composite foundation and reduce the settlement after work completion. The method has simple construction process and strong operability, and is convenient for quality control and detection; and the pile-soil coordinated interaction effect ofthe formed composite foundation is good.