The effects of various surface treatments on the friction and wear properties of AZ91D magnesium alloy substrate against the SUJ2 steel ball were evaluated by using a horizontal reciprocating friction and wear test apparatus. The friction and wear properties greatly changed due to the type of surface treatment in spite of being under equal friction and wear testing conditions. Wear loss of AZ91D magnesium alloy anodized from the phosphate solution was greatly reduced in comparison with the other surface treatment such as Dow17, conversion coatings and also no surface treatment. The above results suggest that anodizing from the phosphate solution should improve the friction and wear properties of magnesium alloy used for sliding parts.