Variable cycle engines generally have multiple working lines to achieve the performance requirement of multiple working modes， transforming the Core-Driven Fan Stage （CDFS） from the conventional compressor line-oriented design to face-oriented design. Based on CDFS experimental efficiency with the angle adjustment of Variable Inlet Guide Vanes （VIGV）， a mass flow-reduction and pressure ratio-reduction design method is proposed to balance different working modes performance. The method lowers the rotor and stator aerodynamic load， and raises the reaction. Numerical simulation of a CDFS with reduced design mass flow of 3.2% and design pressure ratio of 5.0% showed that the efficiency and surge margin decreased by 0.5% and 2.2% respectively in the single bypass mode， and increased by 1.4% and 4.7% respectively in the double bypass mode. The performance profits of the double bypass mode exceeded the losses of the single bypass mode. Comparison of stage characteristics revealed that the performance profits of the mass flow-reduction and pressure ratio-reduction method originated from the improvement in the VIGV and stator total pressure recovery coefficient. Based on the priority of engine performance requirements in different working modes， and the advantage of adjustable CDFS work point through the forward variable area bypass injector， the mass flow and pressure ratio-reduction design method is feasible with high application potential.