The laser surface cladding of AZ91D magnesium alloy with Al + Al2O3 powders was investigated. X-ray diffraction (XRD) was used to identify the phases in the laser cladding layer, and the growth morphology of the boundary zone between the laser surface cladding layer and AZ91D substrate was observed by optical microscope and scanning electron microscope (SEM). The elements mapping scanning analysis on the boundary zone were carried out with energy-dispersive spectrum (EDS). The results showed that the distribution of the Al2O3 particles was homogeneous in the laser surface cladding layer; the growth morphology of the boundary zone was found to be in a unique parallel-branching feature. The temperature gradient, the liquidus temperature, the rate of dendrite growth and the rate of pool solidification on the growing fronts affected its formation. Furthermore, compared with the AZ91D substrate, the wear resistance of the laser cladding coatings was improved.