The invention belongs to the technical field of detachment of beret pieces of cast-in-situ box girders, in particular to a simple lifting device for detaching beret pieces of a box girder and a method. The simple lifting device for detaching the beret pieces of the box girders comprises a main beam, wherein the fixed end of the main beam is connected with the top part of the box girder; the suspending end of the main beam extends out of the box girder; the length direction of a main beam is vertical to the length direction of the cast-in-situ box girder; a first fixed pulley and a second fixedpulley are sequentially arranged on the main beam from the suspending end to the fixed end; a reserved hole is formed in one side of the second fixed pulley; a first winch and a second winch are fixedly arranged on the main beam. The simple lifting device has the advantages that the detachment efficiency is high, and the convenience in use is realized.