Abstract: To ensure the safe, stable and long-period operation of the steam turbine unit in chemical plant and bring more economic benefits to the factory, meticulous maintenance and operation of the process is needed. More importantly, reliability based maintenance shall be provided and maintenance time shall be shortened to achieve the goals of prolonging the shutdown maintenance intervals and ensure the long-period and stable operation of the unit when faults occur. Combining with troubleshooting and technical transformation of the turbine oil seal and instrument circuit, this paper reveals the importance of reliability based maintenance of the turbine.