Abstract: The 660MW ultra supercritical cogeneration unit of a company adopts the high and medium pressure split cylinder double extraction adjustable heating steam turbine independently designed and produced by China, and is designed with the high-pressure cylinder pre heating system. The time from cold start to warm-up of the steam turbine reaches 265min, resulting in an increase in the start-up cost of the unit. Through systematic research and analysis, the power plant optimizes the original steam turbine pre heating system, adds the IP cylinder pre heating system, pre warms the unit under the turning state of the unit, shortens the impulse starting time of the steam turbine from 265min to about 23min, and greatly reduces the start-up cost of the unit.