<p>In order to enhance the combustion of fuel and air in scramjet combustor, numerical simulation of scramjet combustor with five different wall divergence angles and five different wall divergence positions was carried out. Unsteady Reynolds-averaged Navier-Stokes equations and shear stress transport <i>k-ω</i> turbulence model are used to deal with turbulence, and finite rate/eddy dissipation model combined with global reaction mechanism is used to deal with turbulent-chemistry interaction. Firstly, the reliability of numerical simulation method is verified and validated by grid independent study and experimental case study. Then the results of shock wave system, recirculation region, Mach number, pressure, temperature, component mass fraction, combustion efficiency and total pressure loss under different wall divergence are obtained by numerical simulation, which fully reflects the influence of wall divergence on combustor performance. The results show that with the increase of divergence angle, the intensity of shock wave system in the flow field weakens, the combustion efficiency decreases gradually, and the total pressure loss decreases gradually. There exist some small divergence angle at which the combustion efficiency is high and the total pressure loss is relative low. For the divergence position, when it is slightly shifted downstream from the reference position, the combustor maintains favorable performance. When the rearward shift of the divergence position increases to a large value, the combustion efficiency increases significantly, but the total pressure loss also increases remarkably, and thermal choking may occur, so the rearward shift of the divergence position should not be too large.</p>