The invention discloses an assembly system for thin parts. The assembly system comprises a 3D printing unit, a carrying unit, a three-dimensional warehouse unit, a feeding unit, an assembling unit, a spray painting unit, a packaging unit and a master control unit, and the three-dimensional warehouse unit comprises a three-dimensional warehouse frame, a stacking machine and a butt joint mechanism; the feeding unit comprises a gantry carrying mechanism, two picking mechanisms, a gluing mechanism, a jacking mechanism, a visual inspection assembly module and two linear conveying lines; the assembling unit comprises a gantry carrying mechanism, a robot, a movable assembling table, a screw driving mechanism and two linear conveying lines; the spray painting unit comprises a transfer robot assembly, a detection table, an overturning table, spray painting equipment, a lifting and pushing mechanism and two linear conveying lines; the packaging unit comprises a butt joint table, a gantry carrying mechanism, a spider hand robot, a material transferring mechanism and two linear conveying lines; and the linear conveying lines on all the units sequentially communicate with one another. The assembly system is formed by a plurality of independent units which are convenient to assemble or disassemble, and is convenient to use and high in automation degree.