It is an instinct requirement of the enterprise management to lower the cost so that the enterprise can optimize the asset efficiency. To enhance competition ability and enlarge the market share, enterprises must have a good inventory management system. In this paper, two solutions of inventory management based on bill of material (BOM) have been discussed. One is the accurate quantity and time that globally decided by primary equation of inventory management and the form of material requirement planning (MRP). The other is the stock requirement quantity and the detail structure which is implemented by compound BOM structure. A systematic and quantitative management method for trivial and heavy stock management had been discussed in this paper.