A chromium free aqueous surface treatment agent for the surface treatment of a single-face electrogalvanized steel plate, formulated by dissolving or dispersing each component in an aqueous medium, wherein the aqueous solution comprises the following components: one or more metallic ion compounds comprising at least one of the ions of Zn z+, Mn 2+ and Mg 2+, wherein the molar concentration of the metallic ions in the surface treatment agent is 0.01-0.3mol/L; one or more vanadium-containing compounds comprising at least one of a compound comprising V 4+ and a compound comprising V 5+, wherein the molar concentration of V element of the one or more vanadium-containing compounds in the surface treatment agent is 0.005-0.08mol/L; one or more compounds comprising at least one of phosphoric acid, pyrophosphoric acid, metaphosphoric acid, phosphonic acid and the ammonium salts thereof, wherein the molar concentration of the P element of the at least one of phosphoric acid, pyrophosphoric acid, metaphosphoric acid, phosphonic acid and the ammonium salts thereof in the surface treatment agent is 0.05-1mol/L; at least one of ammonium fluorotitanate and ammonium fluorozirconate, wherein the molar concentration of the F element of the at least one of ammonium fluorotitanate and ammonium fluorozirconate in the surface treatment agent is 0.01-0.2mol/L; one or more silane coupling agents comprising at least one of vinyl silane coupling agent, amino silane coupling agent, epoxy silane coupling agent and acryloxy silane coupling agent, wherein the molar concentration of the one or more silane coupling agents in the surface treatment agent is 0.1-0.5mol/L; a silica sol comprising silica particles having a particle diameter less than 100nm, wherein the molar concentration of its Si element in the surface treatment agent is 0.01-0.2mol/L; and one or more surfactants comprising at least one of carboxylate, sulfuric acid ester salt, sulfonate and phosphoric acid ester salt, wherein the molar concentration of the one or more surfactants in the surface treatment agent is 0.0001-0.003mol/L; wherein the total solid content in the aqueous surface treatment agent is 2wt%-20wt% of the surface treatment agent. one or more metallic ion compounds comprising at least one of the ions of Zn z+, Mn 2+ and Mg 2+, wherein the molar concentration of the metallic ions in the surface treatment agent is 0.01-0.3mol/L; one or more vanadium-containing compounds comprising at least one of a compound comprising V 4+ and a compound comprising V 5+, wherein the molar concentration of V element of the one or more vanadium-containing compounds in the surface treatment agent is 0.005-0.08mol/L; one or more compounds comprising at least one of phosphoric acid, pyrophosphoric acid, metaphosphoric acid, phosphonic acid and the ammonium salts thereof, wherein the molar concentration of the P element of the at least one of phosphoric acid, pyrophosphoric acid, metaphosphoric acid, phosphonic acid and the ammonium salts thereof in the surface treatment agent is 0.05-1mol/L; at least one of ammonium fluorotitanate and ammonium fluorozirconate, wherein the molar concentration of the F element of the at least one of ammonium fluorotitanate and ammonium fluorozirconate in the surface treatment agent is 0.01-0.2mol/L; one or more silane coupling agents comprising at least one of vinyl silane coupling agent, amino silane coupling agent, epoxy silane coupling agent and acryloxy silane coupling agent, wherein the molar concentration of the one or more silane coupling agents in the surface treatment agent is 0.1-0.5mol/L; a silica sol comprising silica particles having a particle diameter less than 100nm, wherein the molar concentration of its Si element in the surface treatment agent is 0.01-0.2mol/L; and one or more surfactants comprising at least one of carboxylate, sulfuric acid ester salt, sulfonate and phosphoric acid ester salt, wherein the molar concentration of the one or more surfactants in the surface treatment agent is 0.0001-0.003mol/L;