Mo ion implantation at 150 keV in an austenitic stainless steel leads to a pseudo-Gaussian concentration depth profile as predicted by calculation using TRIM code and confirmed by RBS analyses. The structural modification of the implanted layer was investigated using grazing incidence X-ray diffraction (GIXD) for different incidence angles. The X-ray austenite peak depends strongly on fluence and incidence angle, and presents one or two peaks as a function of incidence angle. Using the concentration depth profile of implanted element, the information depth profile of diffracted intensity, and a linear relationship between Mo concentration and lattice parameter, we predicted the γ diffracted X-ray peaks. The experimental X-ray diffraction peaks are comparable to the predicted ones. Mo implantation induces a continuous expansion of austenite lattice, which follows the depth profile concentration in the implanted layer even if the signature of this expansion is the apparition of a new austenite peak.