Abstract: To enhance the mixing of air and combustion gas in the boron-containing solid rocket scramjet and improve the flame stability and combustion efficiency, a backward step-wedge structure was added to the front section of the afterburning chamber based on the lateral intake of primary gas. The impact of the primary gas intake and wedge structure on the combustion performance of the afterburning chamber of the boron-containing solid rocket scramjet were assessed by numerical simulation. The results show that with a constant afterburning chamber structure, changing the distance between the primary inlet position and the step from 0.5d to 6d leads to an initial increase and subsequent decrease in the combustion efficiency of boron particles. At the distance of 1.25d, the combustion efficiency of boron particles peaks at 48%. And the combustion efficiency increases as the primary gas intake angle changes from 45º to 170º. When the inlet angle is 170º, the total combustion efficiency reaches its maximum, which is 71.32%. When maintaining the primary gas intake mode while tuning the ratio of wedge height to step height as 0.40, 0.50, 0.55, 0.60, 0.65, 0.70, 0.75, 1.00 in sequence, the total pressure recovery coefficient decreases as the ratio increases, and the combustion efficiency of boron particles shows an initial rise and a followed decrease, with a peak efficiency of 53.2% achieved at 0.60.