The invention provides an efficient set-retarding and water-reducing agent for cement concrete and a preparation method of the efficient set-retarding and water-reducing agent. The efficient set-retarding and water-reducing agent comprises the following components in parts by weight: 30 to 50 parts of polycarboxylic acid mother liquid, 3 to 5 parts of poly-aluminum chloride, 0.5 to 2 parts of sodium polyaspartate, 10 to 30 parts of allyl polyoxyethylene ether, 0.5 to 0.8 part of coco fatty acid diethanol amide, 5 to 10 parts of hydrogen peroxide, 0.5 to 1.2 parts of mirabilite, 3 to 10 parts of an air entraining agent, 15 to 30 parts of hydrophilic colloid, 1 to 3 parts of a set retarder, 5 to 10 parts of fiber, 1 to 5 parts of asbestos wool, 0.1 to 0.2 part of an initiator and 30 to 50 parts of deionized water. The efficient set-retarding and water-reducing agent is prepared by optimizing the components of the set-retarding and water-reducing agent, modifying part of the components and mixing, so that the efficient set-retarding and water-reducing agent has high compatibility with cement, is small in mixing amount and high in water-reducing rate, can enhance the compression resistance and the fracture resistance of concrete, has a good set-retarding effect, long concrete setting time, high strength and high construction performance, saves construction materials, can save waterand electricity and has high practical value.