Abstract: The Q-branch CARS of N2,O2,H2O and rota tional CARS of H2(S(5) and S(6)) were measured and used to determining temper atures and concentrations of H2 and O2 in a supersonic combustion flame.The Q-branch CARS of H2O were used to obtain the curve of area ratio of resonat and non-resonat CARS versus concentration.The new method of simultaneously measuring CARS of H2 and O2,which was developed in our laboratory,provides a way for simultaneously obtaining temperature and concentration of H2 and O2 in flame,especially for nitrogen free condition.