Abstract: Based on a successful simulation of the mature stage of a typoon, the boundary layer effect on mature typhoon is studied through different comparative numerical experiments. It states that fluxes from the boundary layer make little difference to the typhoon route in 24h but have significant effect on the maintenance of the mature typhoon. Latent heat flux is its main energy source but sensible heat flux has little effect on its maintenance. Momentum flux from the boundary layer has dual effects. Frictional effect enhances the upward movement but weakens the low-level vortex. This is Just like adding an anticyclone convergence field to the lower vortex of the mature typhoon. It can be explained using the boundary layer theory.