We have derived the effect of steady heat flux on the rate of chemical reaction based on the line‐of‐centers model using the explicit velocity distribution function of the steady‐state Boltzmann equation for hard‐sphere molecules to second order. We have found that the second‐order velocity distribution function plays an essential role for the calculation of it. This indicates the significance of the second‐order coefficients in the solution of the steady‐state Boltzmann equation as terms which reflect the local nonequilibrium effect. © 2004 American Institute of Physics