Tap water cooling and afterheat recovery system and method for data center

The invention discloses a tap water cooling and afterheat recovery system and method for a data center. Cooling treatment to the data center is performed by a freezing water group; a tap water group is adopted to assist the freezing water group for cooling the data center; according to different tap water temperatures, cooling of the data center is realized by an alternate cooling way of the freezing water group and the tap water group, so that self temperature of the tap water is fully utilized to lower freezing energy consumption of the data center and the energy consumption in domestic hot water preparation, and the purpose of saving energy is fulfilled; a water return loop of the freezing water group is cooled by a cooling water group, and the cooling water group is subjected to heat exchange and then is subjected to secondary cooling through the tap water group, so that the tap water group is fully utilized to realize cooling and afterheat recovery; and by performing heat recovery on the cooled tap water