Laser alloying of magnesium alloy AZ91D with direct Al-Si power feeding for improvement of corrosion resistance was investigated. The relationship between laser alloying parameters and dimensions of alloyed layers was studied. The microstructural features of the alloyed layer were characterized by using scanning electronic microscope (SEM), energy disperse spectroscopy (EDS) and X-ray diffraction (XRD). Anodic polarization test was applied to evaluate the corrosion performance of AZ91D alloyed layer, which yielded enhanced corrosion resistance. The contribution of the intermetallic compounds (IMCs) of Mg2Si, Al12Mg17, Al3Mg2 in alloyed layers to corrosion resistance was studied.