The invention relates to a quick switching control method and a control device for a concentrated bypass type parallel UPS, and aims to detect voltage of each UPS module; at least two detection points are set in each UPS module, and respectively correspond to an alternating and direct current input end or output end in the UPS module and a middle connection line; when a voltage signal of at least one of the detection points is an abnormal signal, the UPS module is abnormal; and when all the USP modules are abnormal, an output is switched to a bypass for outputting. The control mode can accurately and quickly judge the switching operation moment, so that the judgment duration is greatly shortened, the phenomenon that the UPS output and the bypass output have short circuit for milliseconds is avoided, and the phenomena of damage to a UPS device, tripping of a bypass input switch and the like are avoided.