The invention relates to a cam climbing mechanism. A motor and a speed reducer are connected and are installed on a machine frame together, an output shaft of the speed reducer is provided with a driving sprocket, a first cam shaft is installed through a bearing in a bearing bracket which is located at one end of the top of the machine frame, a first sprocket is fixed arranged on the first cam shaft, and a short chain is sleeved on the driving sprocket and the first sprocket. A second cam shaft is arranged in a bearing bracket which is located at the other end of the top of the machine frame through a bearing, a second sprocket is fixedly arranged on the second cam shaft, and a long sprocket is sleeved on the first sprocket and the second sprocket. The lifting frame is placed on the machine frame, and a limit guide mechanism which enables the lifting frame to move in a lifting mode is arranged between the lifting frame and the machine frame. Work piece supporting plates are respectively arranged at two ends of the top of the lifting frame, support wheels are respectively arranged at two ends of the bottom of the lifting frame, and support wheels which are arranged at two ends of the bottom of the lifting frame are respectively arranged on an eccentric cam of the first cam shaft and an eccentric cam of the second cam shaft. The cam climbing mechanism has the advantages of being reasonable in structure, capable of achieving stable ejecting or descending of a tool support, constant in journey, safe and reliable.