Disclosed is a synergistic herbicidal composition comprising a compound A and a compound B; wherein the compound A is one selected from the group consisting of clethodim and sethoxydim; wherein the compound B is one selected from the group consisting of thifensulfuron-methyl, tribenuron-methyl, cyclosulfamuron, bensulfuron-methyl, triasulfuron, mesosulfuron-methyl, monosulfuron, amidosulfuron, metsulfuron-methyl, chlorsulfuron and nicosulfuron; and the weight ratio between the compound A and the compound B is in the range from 100:1 to 1:100. The novel composition obtained by binary combining achieves a synergistic effect in controlling monocotyledonous weeds, dicotyledonous weeds and Cyperaceae weeds in the fields of resistant rapes and resistant soybeans.