The effects of RE and Ca on the mechanical properties and corrosion behavior of AZ91 have been studied by Zwick electronic universal material testing machine, X-ray diffraction, corrosion test and polarization experiment. The results showed that the addition of RE and Ca could improve the mechanical properties and corrosion resistance of AZ91 alloys. The ultimate tensile strength of AZ91 with addition of 1%RE and 1%Ca increased by 15.9%. The addition of 1%RE in AZ91 made the corrosion rate decrease from 0.453mg·cm-2·d-1 to 0.178mg·cm-2·d-1. Furthermore, with adding 1%Ca in AZ91+1%RE, the corrosion rate of AZ91 decreased to 0.086mg·cm-2·d-1 due to the formation of reticular Al2Ca phases, which acts as an effective barrier against corrosion.