Abstract: As turbomachinary is superior to rocket and ramjet at lower flight speed,a computational analysis of five sorts of hydrogen fueled turbomachinary,i.e.ATR engine,rocket fan,tip turbine fan,two spool hydrogen expander engine and turbofan has been accomplished.The results show that the turbofan with small bypass ratio is superior to the others in the performance at flight Mach number below 3 5.After choice of better cycle parameters,further performance calculation of the turbofan has been carried out.The total residual thrust of six engines is shown to be more than 411 88kN at flight Mach number below 3 5.It is indicated that the specific impulse of the engine is more than 31 63kN·s/kg at flight mach number below 3 5 and 73 55kN·s/kg at flight Mach number below 0 9 respectively.This type of turbofan combined with a ramjet is proved to be suitable for a powerplant in the first stage of a two stage to orbit vehicle.