After the 300MW condensing steam turbine of a power plant was delivered from the factory, it was retrofitted with medium and low pressure conduits for steam extraction and heating, and then the entire flow passage of the whole machine was reformed, and the heating capacity was considered. However, during the heating period, during the process of increasing the steam extraction, it was found that the unit's extraction pipeline and the medium and low pressure ducts were vibrating in the vertical direction. After analyzing and testing the on-site operating data, it was found that the main reason for the vibration was the discharge If the pressure is too low, the specific volume of steam will increase, which will reach the upper limit of the design flow rate of the pipeline at a low mass flow rate. The uneven media flow will cause the backlash motion of the pipeline to be unstable and vibrate, and the mediation control program was not readjusted after the flow part was remodeled. It is recommended that the power plant adjust the mid-range parameters and readjust the mediation control procedures. After the power plant takes advice, the site vibration problem can be resolved.