In this paper, the change of nitrogen at different depths in 35CrMo steel through ion nitriding and laser phase transformation hardening treatments was investigated with Xrays Photoelectron Spectroscopy (XPS). The experimental results show that the deeper oxynitride layer beneath surface can be obtained by the composite treatment process, and the depth of the nitriding layer is also increased. There will be a deeper nitride layer formed through the composite process other than the conventional nitriding process.