Abstract: The wear map is wear mechanism transition relationship of the material in specific contact condition, sliding speed and test load. In the paper, the tests were performed on an AZ91D magnesium alloy using a block (ASTM1045 steel) configuration. The wear rate was measured within a load range of 98~490 N and a sliding velocity range of 0.083~1.084 m/s. Compositions, morphologies and microstructure of worn surfaces or section and wear debris were characterized by scanning electron microscope, electron microprobe analyzer and X-ray diffraction. The wear mechanism of thixoformed AZ91D magnesium alloy was studied and its wear map was plotted in dry sliding condition. The results show that wear behavior of thixoformed AZ91D magnesium alloy in dry sliding condition can be divided into mild wear and severe wear. The former, at stable stage, saw a thermal balance effect for the contact surface temperature and the mass loss was proportional to sliding distance. Whereas in severe wear regime, wear loss dramatically increased with sliding distance. The mild wear, including oxidation and abrasive and delamination wear, which gradually developed in order and their wear rates were comparable. While the severe wear was mainly caused by severe plastic deformation and melt wear, and the transition of wear mode produced a rapid increase of wear rate. Furthermore, the contact surface temperature had a function with expression (F^1/4V^1/2) and the transition temperature was about 75 ℃±5 ℃ from mild wear to severe wear excluding melt wear in tests.