The utility model discloses a no computer lab elevator top layer examines and repair uses cat ladder, the cat ladder includes user state and idle state, works as when the cat ladder is in the user state, the one end and the spandrel girder of elevator well of cat ladder are connected, the other end of cat ladder is placed in the sedan -chair top of elevator, when when the cat ladder is in idle state, the cat ladder is fixed in on the elevator well. The utility model discloses a no computer lab elevator top layer examines and repair the cat ladder, and what dimension guarantor person can be very convenient detects and tie up the guarantor to installing too high top layer parts like hauler, overspeed governor etc. Can not result in because of the difference in height carrying out regular dimension guarantor's work.