The invention discloses a clamp used in the machining process of machine parts. The clamp is characterized in that the left side and the right side on the middle part of a base platform each are fixedly connected to a vertical beam; a base of a hydraulic cylinder is fixedly connected to the right end of the vertical beam on the left side, and a piston rod end of the hydraulic cylinder is fixedly connected to a movable pressing plate which is vertically arranged; a groove which is sunken rightwards is formed in the middle of the left side of a fixing clamping block, the cross section of the groove is a toppled trapezoid, and the long edge of the trapezoid is located at the left end; an upper clamping part and a lower clamping part which are vertically arranged are arranged at the positions,located at the upper part and the lower part of the groove, of the fixing clamping block respectively; and the upper part and the lower part of the movable pressing plate are matched with the upper clamping part and the lower clamping part respectively, the right end face of the movable pressing plate is a corrugated surface, and the upper clamping part and the lower clamping part both are provided with corrugated surfaces. The clamp can clamp various machine parts, and is good in universality.