Abstract: A check valve for low pressure operating conditions includes: a valve cover, a valve body, and an upper diaphragm between the body and the cover. A first pressure cavity is provided on a lower surface of the valve cover and used for accommodating a backward direction medium, a second pressure cavity is machined on an upper surface of the valve body, within which an inflow passage and an outflow passage are provided, an inflow hole is machined from an inner wall of the inflow passage to a bottom face of the second pressure cavity, and a medium enters into the second pressure cavity from the inflow passage via the inflow hole, and applies upward pressure on the upper diaphragm. A backflow channel in communication with the first pressure cavity is machined on a side wall of the outflow passage.