The purposes of this research were to study the waste, causes of waste, and waste reduction of supply chain in process of automotive spare part’s inventory. The findings found that the waste of supply chain in process of automotive spare part’s inventory in warehouse were inventory counting before storage and inventory classifications which were activities without value added but needed for operation. Causes of waste consisted of 4 aspects: 1) people or employees, 2) tools and spare parts, 3) process, and 4) environment. Guideline formulation of waste reduction is the training on product assignment, provision of a place for supporting fragile items, application of technology in inventory system in order to brighten and ventilate.