The invention discloses a rainwater utilization system of a green belt and a construction method, relates to the field of municipal public projects. The rainwater utilization system for the green beltincludes a drainage tube for gathering and draining rainwater and a water storage and seepage tank. The water storage and seepage tank is embedded in planting soil corresponding to the green belt andis provided with a side plate, a top plate and a bottom plate which are connected to form a containing cavity, the containing cavity is in communication with a water outlet of the drainage tube, anda water seepage part is arranged at the end, close to the top plate, of the side plate, so that water in the containing cavity is capable of permeating into the planting soil only through the water seepage part; and an overflow port is formed in the end, close to the top plate, of the side plate, and the overflow port is in communication with a rainwater conveying system. By means of the rainwaterutilization system of the green belt and the construction method, automatic, long-lasting and stable water supply to roots of plants in the green belt is achieved through the self-seepage effect; andmeanwhile, the structure is simple, and no additional controller or other components are needed after installation. Compared with the prior art, the rainwater utilization system has the advantages ofbeing small in maintenance workload, long in service life and low in construction cost, and is suitable for large-scale promotion.