Abstract: A pump with a pressure driving head comprises a retaining tube; the retaining tube having a receiving space; liquid can flow therein; a returning element being installed in the receiving space; a movable tube received in the receiving space of the retaining tube; a head extending from a top of the movable tube; the head having an outlet which is communicated to the movable tube; when a pressure is applied to the head, the movable tube will move axially in the retaining tube; and an isolation device tightly adhered upon an inner wall of the receiving space of the retaining tube; an air isolation chamber being formed by the isolation device and the movable tube; with the pressing affect of the movable tube, a part of liquid in the retaining tube will be stored in the air isolation chamber so as to be formed with an air isolation layer.