This disclosure provides a chilled water cooling system. The chilled water cooling system includes a natural cooling circuit and a mechanical cooling circuit. The natural cooling circuit includes a natural cooler, a chilled water main pump, at least one first pipeline, and a terminal heat exchanger connected in series. The terminal heat exchanger is disposed at a location in need of cooling. The mechanical cooling circuit includes a chilled water main machine, a chilled water auxiliary pump, and at least one second pipeline connected in series. The mechanical cooling circuit is connected in parallel with the natural cooling circuit through a controllable connecting device.