The invention discloses an improved Brandon steam seal and an application method of the improved Brandon steam seal on a turbine. The improved Brandon steam seal comprises a steam seal arc segment and a spring. A steam guiding groove is formed in the steam seal arc segment. One end of the steam guiding groove is connected with the flow incoming direction of steam. The other end of the steam guiding groove is connected with the back side of a steam seal back arc. The steam seal back arc is embedded in a groove. The spring is arranged at the end of the steam seal back arc so that the steam seal back arc can be supported through elasticity. A sleeve is installed on an end face interface of the Brandon steal seal arc segment. In the starting and shutdown process of a current super-critical and ultra super-critical unit, oxide scale falls off seriously, application of a Brandon adjustable steam seal is affected, a normal opening and closing function can be guaranteed through the improved Brandon adjustable steam seal formed by additionally arranging the sleeve, and the application range is widened.