The steam turbine drive compressor of heavy oil catalytic unit of SINOPEC Zhenhai Refining and Chemical Company was manufactured by SIEMENS in 1970s. The unit has been operating until now and has many problems. However, problems have not been resolved yet after maintenance many times. For the safe operation, the company invited us to overhaul the turbine. However, it has been nearly half a century since the production of the unit. The installation data and relevant data are inadequate. As the technology of HTC three series steam turbines comes from SIEMENS three series technology. Therefore, the maintenance of SIEMENS units can be carried out according to the standards and requirements of HTC. In addition, we have rich experience in this field and completed the overhaul within the predetermined time. The production restarts successfully. The overhaul has a completely maintenance of steam turbine and auxiliary system. The overhaul steam turbine eliminates a series of previous problems and achieves the purpose of maintenance.