This monitor is equipped with double drum,bicable houble piece and double piece and quardruple corearmored cable and is put down into the hole through the orientation of a double-pulley-racl. Its basic principle is combining uttrasonic distance measuring theory with comprter and comprehensive scientific monitoring technology,to execute quality inspection of large diameter foundation pile hole ;that is to monitor hole diameter,inxlination and the thickness of downhole cuttings sediment.