As an effective drag reduction and thermal protection technology, the opposing jet can guarantee the flight safety of the hypersonic vehicle. In this paper, the jet mode transition is realised by controlling the total jet pressure ratio value (PR) with a function. The jet mode transition from the long penetration mode (LPM) to the short penetration mode (SPM) uses an increasing function. However, the jet mode transition from SPM to LPM uses a decreasing function. The flow field reconstruction process of a two-dimensional axisymmetric blunt body model in the hypersonic flow is studied when the jet mode transition between SPM and LPM changes into each other. The flow field structures and wall parameters of the LPM and SPM transition processes are obtained. The results indicate that the drag and Stanton number both decrease in the transition stage from LPM to SPM, and this is beneficial for the improvement of the drag reduction and thermal protection effect. The peak values of drag and Stanton number fall by 36.39% and 46.40%, respectively. When the jet mode transforms from SPM to LPM, the Stanton number increases, and the drag force first increases and then decreases. However, the final drag reduction effect is not obvious. With the increase in the change rate of the total pressure ratio of the two jet transformation modes, the jet mode transition time is advanced, and the flow field changes more violently.