A concrete curing agent, a curing coating layer and a preparation method thereof, the concrete curing agent comprises a hardening agent and a hydrophobic agent, the raw materials of the hardening agent comprises the following raw materials in parts by weight: 0.1-10 parts of fluorosilicate salt and 100 parts of water, and the hydrophobic agent comprises the following raw materials in parts by weight: 0.1-10 parts of a base catalyst, 1-10 parts of a silane coupling agent, 0.1-10 parts of hydrogen-containing silicone oil, 5-10 parts of a cross-linking agent, 10-100 parts of silica sol and 100-1000 parts of water. The present invention can significantly improve the strength, hardness and hydrophobicity, impermeability and freeze-thaw resistance of surface of concrete before and after hardening, and effectively improves the service life of concrete structures.