The invention discloses a single-action vane pump variable adjusting mechanism capable of continuously and proportionally adjusting flow. According to the single-action vane pump variable adjusting mechanism, a traditional hydraulic control variable mechanism is replaced with a closed-loop control variable mechanism containing a ball screw, the ball screw is adopted as the variable mechanism, andthe control precision and the flow control accuracy can be improved by adopting a servo motor. Compared with a traditional piston type variable mechanism, the single-action vane pump variable adjusting mechanism is simpler and more compact in structure, high in response speed and sensitive in action, the response speed and the accuracy of a pump are effectively improved by utilizing the ball screw, and the use value of the pump is improved.