Due to the complex flow in the transitional regime and the nonlinearity of the flow control functions, when a launch verhicle is designed, the aerodynamic heating is predicted mainly by engineering method. The accommodation parameter of linear bridging relation which is used to calculate the heat flux in transitional regime is fixed to fit the blunt cone which is widely used. The results of the bridging relation are validated by using the DSMC method. The validation shows that the accommodation parameter suited for the blunt cone and ensuring the linear bridging relation may be used to calculate the heat flux of blunt cone in a transitional regime.