Although the cost of plastic pallets is higher than wooden pallets, the plastic pallets can be highly reused and exported without fumigating. According to a report by Grand View Research, Inc. The global plastic pallets market is anticipated to grow by 5.2% per year from 2022 to 2030 and the market size is expected to reach USD 9.72 billion by 2030. This research deal with a case study of a plastic pallets manufacturing company in Taiwan. Due to the various product sizes, uncertain demand, long changeover time, limited inventory space, and so on, the case company needs a pragmatic approach to control the inventory level. According to the concept of ABC inventory management, the inventory policy of each class was suggested firstly. Traditionally, it is commonly seen that using increasing class sizes, such as 20%, 30%, and 50% to classify all inventory items. However, the policies will affect the batch sizes, average inventory, number of changeovers, and fill rate. Based on the limitation of the number of changeovers and inventory space limitation, a systematic procedure was proposed to classify all inventory items and maximize the fill rate. Finally, some experiments were tested to give suggestions to the case company.