The utility model discloses a vacuum preloading device that alternating bled, including the drain bar, the bowknot, water drainage branch pipe, two persons in charge, jet pump and efflux pump controller, each drain bar passes through the bowknot and links to each other with corresponding water drainage branch pipe, each water drainage branch pipe arranges side by side, if first row's water drainage branch pipe is 1, the water drainage branch pipe that the second was arranged is 2, similarly, a serial communication port, two persons in charge arrange side by side, one is the first person in charge, be responsible for for the second for one, the water drainage branch pipe of odd number serial number links to each other with the first person in charge, the water drainage branch pipe of even number serial number is responsible for with the second and links to each other, two persons in charge link to each other with a jet pump respectively, two jet pumps link to each other with same efflux pump controller. The utility model discloses can prevent that the too early silt of drain bar is stifled.