Assembly tool and assembly method

According to the assembly tool and the assembly method, it is guaranteed that assembly of a loading and unloading device succeeds at a time, the work efficiency is improved, and telescopic flexibility and mutual non-interference are achieved. The assembling tool comprises a lower side beam assembling assembly, an upper frame assembling assembly and a final assembling assembly, wherein the lower side beam assembling assembly comprises a first supporting pad assembly used for supporting a lower side beam at intervals in the length direction of the lower side beam, a clamp assembly used for clamping two opposite web plates of the lower side beam and a pressurizing assembly used for pressurizing from top to bottom; the upper frame assembly comprises a second supporting pad assembly used for supporting the upper frame, and the second supporting pad assembly is provided with a first positioning assembly used for positioning an upper side beam of the upper frame and the transverse telescopic assembly. The general as