The arrangement of normal drain pipeline in high pressure (HP) heater in a large thermal power unit is unreasonable, which results the vibration of drain pipeline occurred repeatedly and endangers the safety of equipment. Some retrofits are carried out for the normal drain pipeline according to its arrangement in HP heater, such as excluding the water in normal drain pipe by using static pressure difference and condenser vacuum at the initial period of units’ start-up, which could completely eliminate the pipeline vibration, as well as prevent the equipment damage accident caused by vibration. New units could be optimized designed without low-point and U-tube, which could radically eliminate the pipeline vibration caused by small interstage differential pressure.