Abstract: A research on the influence of oxidation on laser irradiating iron was done. Based on the temperature field result, oxidation layer thickness and the quantity of heat in the course of oxidation were computed. Besides, by using multilayer reflective theory, the laser energy coupling coefficient was got with the varying oxidation layer thickness, and the computed value was in line with the experiment result very well. The result indicates that the oxidation heat had little effect when laser irradiated the iron and it could be ignored in engineering application. But the laser energy coupling coefficient may be influenced clearly by the oxidation behavior.