Based on the favorable effect of the elements Al and Si on the improvement in reducing hydrogen permeability, a new combined process of simultaneous aluminizing and siliconizing, followed by oxidizing treatments using double glow plasma technology on 316L substrate was developed in this work. Microstructure and phase structure of as- prepared coating was examined by scanning electronic microscopy (SEM), X-ray diffraction analysis (XRD), transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS), respectively. The results showed that the simultaneous aluminizing and siliconizing coating consisted of an outer aluminide layer (dissolved Si) and a diffusion zone. After a combined process, a continuous and compact Al2O3-rich coating was formed at the outermost surface. SiO2 was also detectable in the oxide coating.