Abstract: Opposing jet flow control technology has a broad application prospect and can achieve effective drag reduction control under the long penetration mode (LPM). In order to further study the opposing jet mode transition mechanism and the influence of freestream conditions on drag reduction control of hypersonic vehicles, wind tunnel tests were conducted on the blunt body model under different freestream total pressures (0.1 and 0.4 MPa), Mach numbers (Ma = 5, 6) and jet total pressure ratios. The structure of the spatial flow field and the surface pressure distribution of the model were obtained by using high-speed Schlieren and electronic pressure scanning valve. The results show that the LPM is extremely unstable, with strong unsteadiness and asymmetry, and the flow field presents axial and radial oscillations. At the transition phase, the flow field oscillates axially and changes continuously between LPM and short penetration mode (SPM). The SPM is stable and the flow field structure is axisymmetric. As the total pressure ratio increases, the surface pressure distribution of the model corresponds to the phase of jet mode transition. The critical total pressure ratio of the jet is affected by the freestream total pressure and Mach number. As the freestream total pressure increases, the critical total pressure ratio increases, and the total pressure ratio interval corresponding to LPM becomes larger. With the increase of incoming Mach number, the minimum total pressure ratio and critical total pressure ratio of sonic jet decreases, and the total pressure ratio interval corresponding to LPM becomes smaller.