The invention belongs to a precast beam water-saving curing method and a curing device thereof. The curing method comprises the steps of constructing a temporary precast beam yard, preparing an inflatable curing shed, preparing a precast beam, preparing before curing and curing the precast beam. The device consists of a water suction pump, a water pump with a time control solenoid valve, a water supply tower and a reservoir, wherein the inflatable curing shed is used for forming a spray curing space which can be quickly built and detached and isolated from the outside at the periphery of the precast beam to carry out uniform moisture-preservation and heat-dissipation curing on the precast beam; horizontal and longitudinal inflatable tubes distributed at intervals and communicating with each other at intersections form a supporting framework of the inflatable curing shed; and an agricultural irrigating water hose is fixed on the inner peripheral wall of the inflatable curing shed by fixing ropes. The curing method and device have the advantages of reasonable design, water saving and environmental protection, less personnel, good curing quality of the precast beam, high constructionefficiency and good use effect, and are economical and practical and safe and reliable.