The　in-vitro　degradation　behavior　and　corrosion　mechanism　of　Mg-4.0Zn-0.2Mn-0.2Ca　(wt%)　micro-tube　was　investigated　by　the　immersion　tests　and　electrochemical　tests.　The　results　show　that　the　corrosion　resistance　of　the　micro-tubes　can　be　improved　by　the　annealing　treatment.　The　long-term　immersion　tests　reveal　that　the　corrosion　process　is　relatively　uniform,　and　the　corrosion　rate　of　the　annealed　micro-tube　in　Hank＇s　solution　is　about　0.30　mm/a.　During　the　initial　stage　of　immersion,　Mg(OH)2　is　formed　on　the　surface　of　the　annealed　micro-tubes,　forming　a　protective　film　to　hinder　the　corrosion　progress.　Although　the　formed　hydroxyapatite　(HA)　on　Mg(OH)2　film　can　further　reduce　the　corrosion　rate,　the　coarse　secondary　phases　in　Mg　matrix　can　enhance　the　galvanic　corrosion　effect.　The　generated　abundant　hydrogen　may　destroy　the　HA　film,　thus　promoting　the　corrosion　process.　Copyright　©　2022,　Northwest　Institute　for　Nonferrous　Metal　Research.　Published　by　Science　Press.　All　rights　reserved.