All speeds control equations were deduced from traditional compressible equations with precondition method and applied to 2D inviscous/viscous flows at all speeds. Jameson central difference scheme, LU-SGS implicit iterative method and round-off control were used to accelerate convergence rates and improve numerical precision. Computations were carried out in the bump flow in a channel, viscous cavity flow and chemical non-equilibrium flow. Numerical results were compared with standard cases. The methods and programs proved to be precise and credible. All these will serve as foundations for further study of integrated flow in combustor and nozzle.