The invention relates to an ultralow-pressure precise pressure reducing valve and overcomes the defect the existing pressure reducing valves cannot generate ultralow pressure in the prior art. The middle of the upper cover of the pressure reducing valve is threadedly connected with an adjusting magnetic shaft seat. An active magnetic piece is fixedly mounted on the lower portion of the adjusting magnetic shaft seat. An air inlet nozzle and an air outlet nozzle are disposed on a pressure vessel. A support is mounted on the pressure vessel. A force transmission lever is mounted on the support through an elastic pin. A seal piece and a central screw are respectively fixed at two ends of the force transmission lever. The mounting position of the seal piece corresponds to the position of the air inlet nozzle. The middle of a pressure film is mounted on the central screw. A limit magnetic seat piece is fixedly mounted above the pressure film through the central screw. A passive magnetic piece is fixedly mounted above the limit magnetic seat piece. The passive magnetic piece and the active magnetic piece have the same polarities opposite to each other and the mounting positions of the two correspond to each other. The diameter of the pressure film is 200mm. By the pressure reducing valve, precise pressure reducing of ultralow-pressure is achieved via the large-diameter pressure film.