Increasing competition in the oil sector, the company must make improvements to maintain the company's stability in achieving its vision. One factor that needs attention is the preventive maintenance system. PT. Petrochina International Jabung Ltd is one of the companies engaged in the field of Oil and Gas located in East Tanjab District, Kec. Geragai This analysis discusses the Reliability and Determination of the Air Dryer Components inventory needed to determine reliability in the event of a breakdown of spare parts. This problem is solved by a method of reliability by applying the Weibull Distribution Damage rate function to determine the amount of critical component inventory within one year. The results showed that all critical components were distributed to Weibull. Based on the critical components that have been determined by the ABC method is associated with the function of the rate of damage to the reliability method, the inventory for critical components over a one-year period for each critical component is Pre Filter and After Filter as many as 4 optimal ordering units (Q *) and 2 units of ordering points return (r).