Abstract: Numerical simulations were performed on premixed stoichiometric hydrogen-air flowfield around hypervelocity conical projectile based on finite-volume Navier-Stokes(N-S)equations considering chemical reaction to study shock-induced combustion with a variation in free-stream conditions and projectile diameter. The numerical methods were the second order time accurate LU-SGS scheme and Steger-Warming flux Jacobian splitting with chemical reaction source diagonalized implicitly. As a first step of validation procedure, simulation of Lehr's experimental result was carried out to confirm the reliability of the method mentioned above, including the examination of the appropriateness of grid by grid refinement study. As a final step, the effects of the projectile flight Mach number(Ma=4.18, 5.11, 6.46) and the diameter(D=5, 10, 15 mm) on the stability of hydrogen-air combustion flow field were tested. Results show that, the grid refinement has great effect on hydrogen-air combustion flow structure, and the combustion field becomes more stable with increasing projectile Mach number and reducing diameter.