In recent years, some new type steam seal have been used in retrofitting of flow passage of stream turbine. It is worthy of studying the heat economy of various steam seal and operation status of retrofitted units. According to steam seal retrofitting results of ten units in Hunan province in 2010, the safety of different steam seal during start up, heat economy before and after transformation and timeliness are analyzed and summarized. The recommendations are valuable to similar transformation of the power plants.