An online monitoring system of turbine oil was developed，and its related system was introduced.The viscosity，density，temperature，percentage of water content，particle concentration of turbine oil can be monitored online by this system，and all test parameters can be uploaded to the workstation PC through network sequentially，and they can also be stored and analyzed in workstation.The new turbine oil was used as sample oil in experiment to test the properties of the monitoring system.The test results of temperature and viscosity by the system were compared with that of test in laboratory.The results show that the system is stable for online monitoring of turbine oil，and the experiment result shows a relative high precision.Therefore，this system is adequate to the application of practical industrial environment.