Abstract: Before installing tractor transmission system into whole tractor，transmission system needs to be dialyzed and filtered to remove impurities generated during installation or operation of transmission system，so as to improve service life of the transmission system.At present，dialysis and filtration methods used by different tractor manufacturers in the market are also different，selection of filters and time of filtration and dialysis are also different，and effect is naturally different.Through comparative analysis of dialysis and filtration methods commonly used in market when tractor transmission system runs in online，and according to limit value of transmission system for cleanliness of oil and actual application，filter accuracy was put forward in corresponding filtration and dialysis methods，hoping to provide some help for development of agricultural machinery industry.