Abstract: In this study, the effects of the structural parameters of the V-shaped flameholder on the combustion characteristics of the dual-mode scramjet combustor under low Mach number conditions were analyzed via by numerical simulation. The results show that the V-shaped flame holder easily forms a geometric throat in the airflow, which limits the expansion and connection of the flame, thereby affecting combustion efficiency. By optimizing the size, position, and number of flameholders, the local Mach number can be reduced from 2.25 to 1.6, and the pressure rise region can be expanded to 860 mm. Alternatively, by adding injection points on both sides of the flameholder and igniting fuel, the Mach number near the flameholder can also be reduced from 1.6 to less than 1. This can generate a pressure rise on the wall surface, form thermal resistance, weaken the interaction between the shock wave and boundary layer, effectively compress the surrounding airflow toward the center of the combustion chamber, mitigate the adverse effects of the geometric throat, increase combustion efficiency by more than 15%, and improve both the uniformity of the fuel distribution and the extent of the pressure rise region. Through the analysis of the position of the flame holder, it can be concluded that the combustion effect is better when the flame holder is arranged within the 140 ～ 280 mm range of the first expansion section of the low Mach number combustor.