The invention relates to the technical field of water reducing agents, in particular to a polycarboxylate composite enhanced water reducing agent and a preparation method thereof. The polycarboxylate composite enhanced water reducing agent is prepared from components in parts by weight as follows: 2,000-3,000 parts of a polycarboxylate high-performance water reducing agent, 100-1,000 parts of an organic silicone emulsion, 3,000-5,000 parts of acrylic resin, 100-200 parts of triethanolamine, 10-50 parts of a polyurethane rheological agent, 50-300 parts of sodium gluconate and 5-10 parts of an anionic surfactant. With the adoption of the water reducing agent, the cost of concrete can be greatly saved, and the strength of the concrete is significantly higher than that of original concrete.