On the basis of the expanded multi-dimensional Virial equation, the gas equation of state (EOS) is expanded the series to the second term, so that the density effect of real gas can be considered. Using the basic formula of the shock wave and small parameter contained in the Virial equation, the explicit expressions of the gas density, pressure and velocity behind the shock wave changing with the shock wave velocity and the shock wave Mach number are obtained by the perturbation method. The results show that for the same Mach number of the shock waves, compared with the results by the ideal gas model, the pressure, velocity and density behind the waves are all lower, especially the density. With the increase of the Mach number and the density of the gas, the difference in results will be even greater. These relations are the proper corrections to the ideal gas, which reflects the influence of the volume and repulsion effects of the gas molecule, and are fit for the gases whose density is lower than 100 kg·m^-3. The formula of the shock wave for the ideal gas can be regarded as its zero-order approximation. It is very convenient to use these relations to analyze the properties of shock waves.