Abstract: In Computing steady transonic blow, the governing equation is of mixed type.In most part of the computed region, it is of ellip-tic type; while in a region to be determined,it is of hyperbolic type.In this paper, we discuss the relationship between steady equa-tion and tim-dependent equation.On the basis of an analysis based on Jameson's characterstic theory we propose two time-dependent equations and defferent type-dependent splitting methods..Finally we apply these equations and splitting methods to solve transonic small-disturbance equation.Numerical resurts indicate that the me-thod is simple、reliable and converges rapidly.