Low resistance self-discharging backflow preventer

The utility model relates to the technical field of valves, in particular to a low resistance self-discharging backflow preventer which solves the problems of unstable movement, poor safety performance, large energy loss and complex structure of the existing backflow preventer, comprises a valve body and a valve cap arranged at a water inlet end of the valve body, and is characterized in that the middle of the valve body is provided with a water discharging opening; the valve body core part at the water discharging opening is provided with a sleeve; one end of the sleeve, towards the water inlet of the valve body, is provided with a round edge and a spring seat; a third spring is arranged between the external diameter of the sleeve and the inner diameter of the valve body; the valve cap core part is provided with a first check valve; one end of the first check valve is matched with the sleeve; one end of the sleeve, towards the water outlet of the valve body, is provided with a second check valve; the second check valve comprises a slide valve provided with four claws; and the matching part of the slide valve and the sleeve is the width of the four claws. The backflow preventer has the advantages of high partition safety and small head loss when the medium passes through the preventer, and can effectively prevent backflow pollution.