Ducted fans are widely used in unmanned aerial vehicles due to their high propulsive efficiency and safety. The aerodynamics are complex within the vicinity of the ground, including takeoff , landing and hovering. In the present study, the aerodynamic stability of the ducted fan was studied with a modified Moore-Greitzer model to estimate and analyse the stability in ground effect. The model was validated and compared with threedimensional unsteady simulations. The results indicated that the rotating stall occurred for the ducted fan in ground effect. The model results can be used to guide the design and control of the vehicles, to ensure the stability and safety of both the ducted fan and vehicles.