The guidance precision of missile can be affected by aero-optical transmission effect in flow field. In this paper, the hypersonic flow field around sphere-shaped dome was numerically simulated, and the rays propagating through the flow field was also analyzed. Firstly, density distribution of the flow field was obtained. Secondly, the distribution of inhomogeneous refractive index field was determined. Lastly, the path and deflection of the rays propagating through the hypersonic flow field were obtained by tracing rays. The results indicate that, with increasing flight March number, the density and refractive index are increased. It is also indicated that the deflection increases as the distance deviating from the stagnation point of the dome increases and the March number increases.