The invention discloses a reciprocating mechanism of drawing trolleys on a drawing machine. The reciprocating mechanism comprises transmission shafts and a front drawing trolley and a back drawing trolley, wherein the transmission shafts are arranged in a machine base and are driven by a main transmission device; the front drawing trolley and back drawing trolley are arranged on a rail on the upper surface of the machine base; spiral columnar dual-face cams with the same front, the same back and a phase difference of 180 degrees are arranged on the transmission shaft below each drawing trolley respectively; and a fixed idler wheel and a moveable idler wheel are tightly clung to the two sides of working curved surfaces of the dual-face cams when the dual-face cams rotate. The reciprocatingmechanism is characterized in that: a compacting device is an adjustable elastic mechanism; the structure is more reasonable and practical; the advantage of the elastic mechanism is fully used; the defects of lag and poor synchronism are overcome; and the drawing trolleys can alternately clamp pipes to move with the pipes synchronously without a pneumatic system or a hydraulic system.