The effect of the mass ejection on the evolution of the second-mode disturbances in a boundary layer of Mach number of 6 on a blunt plate was investigated by using direct numerical simulation (DNS) method and linear stability theory (LST). Different parameters of the mass ejection and disturbances

such as the ejection velocity

width

location

combination and volume flowrate

were considered. Results showed that: the mass ejection destabilized the two-dimensional and three-dimensional disturbance waves

and the effect was the strongest when the ejection position was close to the lower bound of the neutral curve of disturbances; the volume flowrate was an important factor to determine the effect on the evolution of disturbances; the combined mass ejection had the superposition effect when its volume flowrate was small; the value of N predicted by LST was close to the direct numerical simulation result

implying that LST can quantitatively determine the effect of the mass ejection on the stability of boundary layer.