The invention refers to a kind of positive ion double surface activating agent in third petroleum production chemical oil-displacing agent, who is expressed by m-s-m, m represents the carbon atom quantity of activating agent alkyl radical, s represents the carbon atom of chain connection radical. S=2, 3, 4, 5, 6, m=10, 12, 14, 16, 18, the activating agent can be used singly, it also can be used with other surface activating agent. It needn't add in alkali, thus it is harmless to formation, it saves oil exploit cost, and it is stable, it has excellent property for decreasing the tension of oil/water interface, and overcomes that current oil-displacing agent induces the oil displacing efficiency falling because of the color spectrum detachment phenomenon.