The　creep　behavior　of　the　as-extruded　Mg-8Gd-1Er-0.5Zr　alloy　at　various　temperatures　(150~200℃)　and　stresses　(50~70　MPa)　for　100　h　was　studied.　The　microstructure　evolution　during　creep　was　investigated　by　optical　microscopy　(OM)　and　transmission　electron　microscopy　(TEM),　and　the　creep　mechanism　was　analyzed.　The　results　show　that　the　alloy　exhibits　good　creep　resistance　under　the　experimental　conditions.　The　creep　curves　can　be　divided　into　two　stages:　a　deceleration　creep　stage　and　a　steady　creep　stage.　The　steady-state　creep　rate　is　6.48×10-11　s-1　and　the　creep　strain　is　0.007%　at　the　temperature　of　150℃　and　the　stress　of　50　MPa,　while　the　steady-state　creep　rate　is　4.26×10-9　s-1　and　the　creep　strain　is　0.226%　at　the　temperature　of　200℃　and　the　stress　of　50　MPa.　In　the　case　of　lower　temperature　(150℃),　diffusion　mechanism　acts　as　the　main　control　mechanism,　whereas　dislocation　mechanism　dominates　at　higher　temperatures　(175,　200℃).　Furthermore,　the　precipitates　of　β＇　phase　in　grains　and　the　β　phase　at　grain　boundaries　form　during　the　creep　process.　The　orientation　relationship　between　the　β＇　phase　and　the　α-Mg　matrix　is　(020)β＇//[1010]Mg,　[001]β＇//[0001]Mg.　The　β＇　phase　can　effectively　inhibit　the　dislocation　gliding,　and　the　β　phase　can　pin　gain　boundaries,　both　of　which　play　an　important　role　synergistically　in　improving　the　high　temperature　creep　resistance　of　the　alloy.　©　2019,　Science　Press.　All　right　reserved.