An experimental investigation was conducted in FL-21 wind tunnel to explore cavity flow characteristics.Detailed static-pressure and fluctuating pressure measurements were obtained at the cavity floor to enable the effect of the mass injection at the leading edge to be determined.Results indicate that the difference of the number of mass-injection holes and the flux of mass-injection has no obvious effect on cavity flow characteristics.Mass-injection can reduce the cavity static pressure gradient markedly when the cavity flow type is transitional flow.The study also indicates that the effect of mass-injection on cavity fluctuating pressure distributions has an intimate relationship with Mach number.Mass-injection can suppress the cavity tones effectively at supersonic speeds.