Abstract: Lower reaction was concluded to be a necessary consequence of an increased aerodynamic load of a transonic fan/compressor inlet stage. Through the definitions of aerodynamic load coefficient and reaction, the rule of reaction changing with aerodynamic load coefficient was acquired, and two critical values of aerodynamic load coefficient were given. Based on a successfully designed and tested single stage high load fan, four transonic fan rotor designs were compared through numerical simulation. It was found that with the increase of aerodynamic load coefficient, the distribution of aerodynamic parameters in rotor hub region was changed remarkably. Transonic incoming flow to the stator is determined to be a problem in the design of a high aerodynamic load transonic fan inlet stage. Through discussions, it-s considered that the problem of transonic incoming flow to the stator could be solved by existing design methods. The best design of the single stage fan was picked up, with its aerodynamic load coefficient reached 0.53, and its 3D viscous flow field was analyzed.