This paper investigates the microstructure, mechanical properties and creep behavior of Mg–Al–Ca alloys with different Ca content. SEM and EDAX analyses show that the dominant second phase in the as-cast Mg–Al–Ca alloys is Al2Ca, which distributes at the grain boundaries and disperses in the grain interior as well. Both the elevated tensile strength and the creep resistance of Mg–Al–Ca alloys obviously increased with increasing Ca at high temperature. TEM analyses reveal that finer Al2Ca particles with an average size of 0.02 µm precipitated dynamically during the creep process. Selected area electron diffraction (SAD) patterns show that the dynamic Al2Ca precipitates have a coherent interface with matrix as (0110) Mg // (220) Al2Ca,  Mg //  Al2Ca. The strengthening mechanism of Mg–Al–Ca alloys at elevated temperature was discussed.