A closed circulating water cooling apparatus and method. The cooling apparatus comprises: an internal cooling apparatus, a plate heat exchanger (6), and an auxiliary cooling apparatus. The internal cooling apparatus comprises an internal cooling circulator pump (2) and an air cooler (3). The auxiliary cooling apparatus comprises an external cooling circulator pump (7) and an underground water pipe (8). Internal cooling water flowing through the plate heat exchanger (6) from the internal cooling apparatus exchanges heat with external cooling water flowing through the plate heat exchanger (6) from the auxiliary cooling apparatus. Utilization of the closed circulating water cooling apparatus and method allows for increased cooling capacity, when the environmental temperature is greater than the maximum inflow water temperature permitted by a piece of technical equipment, for the cooling apparatus to still provide sufficient cooling capacity, and for the equipment to obviate any water loss during operation, thus achieving the goal of water conservation.