In order to solve the problem of short service life, frequent leakage, and large amount of water consumption for sealing and washing of 500 thousand tons of methanol project,  the causes of the leakage of the mechanical seal were analyzed, and the type of mechanical seal of the pump, mechanical seal flushing scheme were modified. After the reform, the service life of mechanical seal is prolonged，the requirement of long period operation is achieved and the product cost is reduced.