Cleanliness is a key indicator in the use of hydraulic oil, and its importance is widely valued by equipment manufacturers (OEMs). Some data show that if the cleanliness of hydraulic oil (liquid) is improved from IS04406 20/18 to 15/12, the life of the system will be increased by 5 times. It can be seen that improving the cleanliness of hydraulic oil can greatly extend the service life of the equipment. Hydraulic fluid cleanliness is defined by the size and content of particulate contamination. The hydraulic oil used for general construction machinery loading, OEM requires a cleanliness level of 7 to 9. Water high cleanliness hydraulic oil is produced on the basis of high pressure HM hydraulic oil and is produced under the monitoring of strict multi-stage filtration system and laser cleanliness testing instrument, which can meet the different requirements of users on cleanliness indicators.