Spare parts availability becomes crucial to support maintenance tasks, especially for the continuous process industry. The main purpose of this research is to examine several methods of inventory management that may suitable for spare parts. Examining the demand pattern of the spare parts utilize ABC and ADI-CV classification useful for understanding the type of demand. Spare parts mostly displayed a lumpy pattern, which guides to the possible inventory methods. In general, the three inventory methods: Continuous review, periodic review, and reliability-based methods, provide better performance compared to the existing min-max method currently applied. The higher service level and the lower inventory cost demonstrated by the three proposed methods with no always dominant methods in all cases. Moreover, the reliability-based method provides better performance. The possible reasons due to careful attention to the demand i.e. the optimal replacement policy. This will keep the spare parts requirement consider the reliability characteristics of equipment where it is equipped. This method taking into account the reliability factor, lead time, standard deviation of demand, continuously checking items with a fixed number of orders, and the desired target service level at the beginning of the calculation, which it does not yet have in the existing method.