Gas compressor reliability is vital in oil and gas industry because of the equipment criticality which requires continuously operations. Currently, plant operators often face difficulties in predicting appropriate time for maintenance and would usually rely on time-based predictive maintenance intervals as recommended by Original Equipment Manufacturer. Delayed decision on compressor maintenance intervention has caused prolonged downtime due to poor readiness of spare parts and resources. The paper discussed on development of a software-based tool which is able to assist machinery engineers to quantify performance deterioration of gas compressor and predict optimum time for maintenance activities. Maintenance history data is collected and analysed regularly and maintenance advices are subsequently produced based on the input parameters. Natural gas compressors of an oil producing offshore platform at Peninsular Malaysia are used as a case study of this project. It was found that isentropic efficiency and head decrease, but gas power increases parabolically with time for the low pressure compressors, suspected due to heavy component fouling. From these information, Compressor Performance Monitoring Program is developed which able to compute the fouling level of the compressor in terms of performance indicators deviations. The results are then being utilized to estimate future maintenance requirements based on historical data. In general, this software provides a powerful tool for gas compressor operators to realize predictive maintenance approach in their operations.