Cantilevered stator is widely used in axial flow compressor of small turbojet and axial flow engines, in order to study the effect of cantilevered stator’s gap under different conditions, several different cases including normal and high load, small and medium wheel hub ratio, under certain circumstance are simulated. The results show that similar to cascade, cantilevered stator in compressor has a specific gap which has the best characteristic performance, the existence of gap will deteriorate characteristic performance when there is no root corner stall under high flow condition and design condition, the existence of gap will improve characteristic performance when there is a root corner stall under small flow condition. The leakage flow’s effect on root corner separation brought by the gap is related to the gap’s size and root corner separation’s degree. The gap’s effect trend is unchanged when the compressor’s load is reduced. The best gap’s size seems to be reduced when the wheel hub ratio increases.