The invention discloses an improved covering and uncovering device and method for steel ladle whole process covering. The device comprises four positioning columns welded to the upper part of the outer wall of a steel ladle, rotating shafts of the outer ends of the positioning columns rotationally support a guide seat through supporting rods, the rotating shafts are fixedly connected with an output shaft of a first rotating motor through couplings, the upper portion of the guide seat protrudes out to form a driving seat, a semicircular steel ladle cover is horizontally and slidably connected into the guide seat, a rack is fixed to the middle portion of the upper side of the steel ladle cover, a driving gear is rotationally limited in an inner cavity of the driving seat, a gear of the driving seat is engaged with a rack, a second rotating motor is arranged on the outer side of the driving seat, an output shaft of the second rotating motor passes through the driving seat and is fixedly connected with a driving gear inside the driving seat, and the steel ladle cover can be driven by the second rotating motor to slide horizontally. By means of the improved covering and uncovering device and method, the structure design is reasonable; and in the overall covering and uncovering operation process, manual operation is not required, and the device does not fall down, so that the devicedoes not need to be temporarily removed, and operation is convenient.