In this paper, we propose a method to design an assembly line to correspond flexibly to the global assembly style based on MRP. The precedence relation is separated into vertical and horizontal ones from the Bill of Material (BOM in MRP). The criterion for ordering the part and unit is introduced to determine the order of parts which is not determined by the precedence relations. The assembly line is constructed by the straight line to assemble the unit and by the parallel line to the subunit according to the BOM. In straight line or parallel line, the assembly station is constructed from the several part supplying stations by the criterion that the assembly time is less than the pitch time and the area covering by a man or a robot is restricted.