The invention relates to a reinforcing and toughening agent for concrete, and a preparation method and application thereof, belonging to the technical field of concrete materials. The reinforcing andtoughening agent for concrete in the invention is a composite fiber formed by loading epoxy resin fiber on the surface of a high-strength fiber, and the high-strength fiber is a glass fiber, a carbonfiber, an aromatic amide fiber, a basalt fiber, a polyimide fiber, a polyphenylene sulfide fiber or a polybenzobisoxazole fiber. The obtained reinforcing and toughening agent for the concrete can improve the strength and toughness of the concrete at the same time, and prolongs the service life of the concrete.