The utility model provides a variable cross section pier inspection device to can carry out convenient and fast's inspection operation to the high mound outside of bridge. It includes along the external surface loop of mound to the left side truss that sets up, the front side truss, right side truss and rear side truss, and the setting physically acts on the left side truss in the top at the mound, the right side truss, the front side truss makes it produce power and transmission unit that vertical lift removed with the rear side truss, the left side truss, the front side truss, the inboard horizontal perhaps hoop interval setting of right side truss and rear side truss and the external surface contact's of mound gyro wheel, the fixed cat ladder that accesss to front side truss or rear side truss that is provided with in mound body top.