The invention discloses a wastewater ratio of pressure-adjustable type, which comprises a main value body (12) which is provided with a water inlet and a water outlet (21, 25), and a regulating chamber (26). The water inlet and water outlet are communicated through the regulating chamber. A pressure regulating component is mounted on the regulating chamber. The pressure regulating components comprise a value sleeve (6) and an elastic pulling block. Screws are arranged on the top of the value sleeve. The screw extends into the value sleeve and resists the elastic pulling block. The bottom of the elastic pulling block is provided with a sealed pad (11) for dealing and blocking the regulating chamber. The invention with a matched parameter is arranged on an RO prettified water machine and the pressure limitation force by adjusting the depth of the screw on the top. When being used, particularly, the changes generated by water net pressure or the output water pressure of a booster pump isbigger than the working pressure of the PO filming pipe, the high-handed compressed water which is over the pressure limited value opens the sealed chamber of the regulating chamber from the top of the water inlet chamber on the invented main value body, thus the water entering channel is run-trough. The water is drained from the water outlet and the pressure is automatically reduced.