Abstract: The high temperature behind the extremely supersonic flow shock layer leads to the excitation of internal energy mode and accompanied by thermal radiation. The high temperature makes the air molecules completely dissociated, and the contribution of atomic components to radiation will reach more than 80%. Based on the optimized atomic radiation model and using the photon tracing direct simulation Monte Carlo (DSMC) method, the wall radiation heating of hypersonic two-dimensional cylinder at different Mach numbers in the rarefied flow region is studied. The wall pressure and heating with or without excited radiation effect and the translational, vibrational and rotational temperatures along the stagnation line are obtained. Without considering the excitation radiation effect, the wall pressure and heating obtained are in good agreement with the previous simulation results and the error is less than 5%. Especially at the stagnation point, the error is less than 1%. The translation, vibration and rotation temperatures obtained are also in good agreement with the literature results. Under the same flow conditions, considering the radiation effect, it is found that when the flow velocity is lower than 10 km/s, the radiative heating is not obvious. While the flow velocity is greater than 10 km/s, the proportion of radiative heating to convective heating will exceed 30% in the stagnation point. After considering the radiation effect, the maximum values of translational, rotational and vibrational temperatures in the non-equilibrium region have little effect. In addition, another important conclusion is that the concentration of atoms in the flow field is an important factor affecting the magnitude of the radiative heat flow on the wall.