The invention discloses a concrete external curing agent, which belongs to the technical field of building materials. The external curing agent for concrete developed by the present invention is mainly composed of β-sitosterol, phospholipid, water, vegetable oil, drying oil, polyallylamine, defoamer and calcium bicarbonate, and after first stirring and mixing the β-sitosterol and phospholipid , pour into the preheated vegetable oil, then add dry oil to obtain an oil phase; stir and mix water and polyallylamine, then add calcium bicarbonate, preheat to obtain a water phase; Add the oil phase to the water phase. After the oil phase is added, add the defoamer, continue stirring and mixing at a constant temperature for 40-60 minutes, discharge, and fill to obtain the concrete external curing agent. The product developed by the invention has good storage stability, can significantly improve the performance of the concrete after curing, and does not cause secondary pollution to the environment after use.