The invention belongs to the technical field of building overall structures and particularly relates to a construction method for connecting floor slabs and wall surface joints of a multilayer light steel structure building. The construction method is characterized by comprising the following steps of (1) modular production of floor slab structures of the light steel structure fabricated building,(2) modular production of wall surface structures of the light steel structure fabricated building, and (3) connecting forms of the different floor slabs and different wall surface structure modules.The joints are simple in structure and convenient to mount, integrity is good after completion, and connecting is firm, also durable and stable; seam mounting parts are concealed inside seams, thus the attractiveness of surface decoration is not affected, and the seams can also be arranged in the junctions of the wall surfaces and the floor slabs; the joints do not affect passing and connecting of water and electricity pipelines pre-arranged in the floor slabs; and through the connecting method of the joints, the problem that when the area of the single floor slab is large, the length and thewidth exceed the limits, and consequently, the floor slabs cannot be transported is solved.