Al-Ni-Y-Co　and　Al-Ni-Mm-Fe　amorphous　and　nanocrystalline　composite　coatings　were　prepared　on　the　surface　of　AZ91　magnesium　alloy,　by　automatic　high　velocity　arc　spraying　system.　The　microstructures　of　the　composite　coatings　were　analyzed　by　scanning　electron　microscope　(SEM)　and　X-ray　diffraction　(XRD).　The　results　show　that　the　composite　coatings　compose　of　amorphous　phases　and　crystalline　phases.　The　composite　coatings　have　a　compact　structure　with　low　porosity.　The　Vickers　microhardness　HV　of　Al-Ni-Y-Co　and　Al-Ni-Mm-Fe　coatings　is　3117.6　MPa　and　3407.2　MPa,　respectively,　which　is　about　four　times　higher　than　that　of　the　traditional　Al-RE　coatings　and　five　times　higher　than　that　of　the　AZ91　magnesium　alloy.　The　electrochemistry　experimental　results　show　that　the　corrosion　resistances　of　the　Al-Ni-Y-Co　and　Al-Ni-Mm-Fe　amorphous　and　nanocrystalline　composite　coatings　are　superior　to　those　of　the　traditional　Al-RE　coatings　and　AZ91　magnesium　alloy.