The on-line monitoring of mining shearer oil can detect the running state of its transmission system.The pollution stage of lubricating oil was divided according to the oil change standard of industrial closed gear oil for the first time,and the wear particle morphology in coal mining oil was studied.The research shows that the service life of the lubricating oil in the shearer transmission system can be divided into 6 stages:unused period,lightly polluted period,sub lightly polluted period,sub heavily polluted period,heavily polluted period and scrapped period.The particle morphology of unused coal mining oil was studied.It is found that there are particles even in unused lubricating oil,and the particle size is below 5 μm,it will affect the evaluation standard of lubricating oil.When setting the monitoring parameters of the oil wear debris of the shearer transmission system,several wear debris particle size nodes,30 μm,50 μm and 70 μm,should be paid attention.When the abrasive particle size in the oil is less than 30 μm,the shearer is in normal operation stage of shearer.When the particle size of wear debris in the oil is mostly 30 μm to 50 μm,the shearer is in normal operation stage,but a certain amount of new lubricating oil shall be added.When wear debris from 50 μm to 70 μm appears in the oil,the lubricating oil can be replaced and the transmission system can be overhauled.When the particle size of wear debris is more than 70 μm,the transmission system can be overhauled.