The invention discloses a cascade SVG water cooling control method which comprises the following steps of 1) carrying out real-time temperature sampling on a plurality of module units in cascade SVG,sending the temperature data obtained through sampling to a module control board; 2), the module control board transmitting the received temperature data to a SVG main controller; 3), the SVG main controller processing the temperature data and controlling the running mode of a water cooling host, wherein each switching of operation mode has a hysteresis width. The invention provides a cascade SVGwater cooling control method to reliably adjust water-cooled SVG, and a fault module can be accurately positioned. The heat dissipation faults of the individual modules are differentiated from the integral temperature control of the cascade SVG, so as to prevent error control caused by interference and other factors.