This paper analyzes the inventory management system of spare parts for Locomotive Depot-Sofia. Considering the large inventory park of the depot, mainly the repair works related to the electric locomotives, series 44, 45, 61, as well as diesel-hydraulic locomotives, series 52 and 55 were considered. The periodicity of planned inspections and repairs is determined on the basis of traveled kilometers or working days. Exploitational inspections are provided for in the locomotive turnover schedule. In order to make an optimal delivery of spare parts in Locomotive Depot-Sofia, it is necessary to carry out analyzes and choose a system for managing the inventory. The decrease in the average availability of spare parts is related to an increase in the number of deliveries during the year, respectively a decrease in the quantity in one delivery. The higher the number of deliveries during the year, the higher the costs of deliveries. Inventory management is related to determining the optimal quantity in one delivery, as well as the optimal number of orders that will balance both types of costs and minimize them without affecting the continuous production.