Hydraulic oil is the direct medium of the hydraulic system, the power and operation control of the hydraulic system are transmitted by hydraulic oil, the main parts of the hydraulic oil "deterioration" are the hydraulic oil tank liquid jade oil filter, hydraulic parts (such as: hydraulic pump, hydraulic motor, various control valves, etc.) wear impurities, etc., the hydraulic oil is used for a long time is not replaced. The impurities in the hydraulic oil (iron filings, copper, dust, etc.) will accumulate more and more, and the fine particle size will become smaller and smaller, such impurities are sometimes invisible to the naked eye. It is small, and it will be easy to pass through the hydraulic oil filter, and the hydraulic oil will be used for too long. The various characteristics of hydraulic oil such as lubrication performance, viscosity characteristics, anti-wear performance, stiffness characteristics, etc., will be reduced a lot, and the impurities in hydraulic oil are brought to the working devices and control components through the working cycle, which directly leads to the rapid wear of the hydraulic components of the entire hydraulic system. The method is to regularly replace the hydraulic oil, or regularly take samples for testing, and it should be replaced in time when exceeding the standard.