An early stage fault diagnosis method based on vibration analysis and oil monitoring was proposed, according to the structural characteristic of the special gearbox used to increase input shaft speed. Through an example of diagnosis for the gearbox of high speed pump, the method was shown effective. By using the diagnosis method based on vibration analysis and oil monitoring, the faults of equipments in early stage can be more precisely estimated. Therefore severe accidents caused by deteriorating condition of the equipment are avoided.