The reasons of mechanical seal leakage of oil pump in Lan-Cheng-Yu pipelines were analyzed,and the main reasons of mechanical seal failure were confirmed,which were the wear of dynamic ring and stator ring caused by impurities,the blocking of flushing pipeline and air blockage.According to the reasons of mechanical seal failure,some improving measurements were put forward,including optimizing the flushing pipeline of the mechanical seal and improving the material of sealing ring.By comparing the filtrate in flushing pipeline,the leakage times and average running time of fault free before and after transformation of mechanical seal,it was proven that the reliability of pumps was improved effectively.In view of the operation of the mechanical seal on the spot,some reasonable improvement measures were put forward,such as installing temperature transmitter to monitor the temperature change of the mechanical seal,improving the exhaust method,and installing differential pressure transmitter in the filters.