An oil metal abrasive particles online monitoring system comprises sensors, a microprocessor and a circuit; each sensor is a solenoid type inductive transducer, and an oil circuit can pass through the solenoid of the inductive transducer; an excitation AC signal-generator is connected with two excitation coils respectively in two totally same sensors, and two induction coils of the two sensors are connected with a signal amplifier; and the signal amplifier, a RMS-DC converter, an AD converter, the microprocessor and a display are in a sequential connection, and the microprocessor is also connected with a keyboard and an alarm. The monitoring system is reasonable in structure, high in sensitivity of monitoring weak signals outputted by the inductive transducer, good in linearity, good in anti-interference capability, stable and reliable in operation, convenient to operate, good in real-time performance, high in measuring precision, and accurate and reliable in monitoring result. The monitoring system can be used in military and civil fields, be used to monitor and diagnose oil pollutant degree and faults of machinery equipment such as various airplanes, ships, automobiles and the like, and the occurrence of various engine accidents is avoided.