The Mg-5Li-3Al-1.5Zn-2RE (LaPrCe) alloy was prepared by hot-chamber extrusion process after casting. The alloy consists of α-Mg solid solution and intermetallic phases (Al11RE3 phase and Al2RE phase). The microstructural analysis of the alloy reveals the correlation between microstructure and creep properties. The stress exponent of n varies from 4.25 to 6.23, and the activation energy varies from 104 to 134 kJ/mol. There is a transition between dislocations climb dominated creep mechanism and dislocation creep controlled by non-basal planes slip. Tensile creep tests were combined with detailed transmission electron microscopy in order to characterize the Al11RE3 phase, which had thermal stability at 448K during the creep test. The dislocations pinned and cross-slip dislocations were observed.