The microstructure of aging Mg-8Zn-1Cu magnesium alloy with Cr, Ce and Sb compound addition was studied by HRTEM. The results show that the hardening rate of the aging Mg-8Zn-1Cu-0.2Cr-0.5Ce-0.5Sb alloy is relatively high in the initial stage of the aging. For the alloy aged at 160 ℃ for 8 h, a number of stacking faults, dislocations and moiré fringe come into existence, and the short rod-shaped pre-precipitates in the grains and the precipitates in the trigeminal grain boundaries are simultaneously formed. For the alloy aged at 160 ℃ for 20 h, its peak hardness reaches 945 MPa and the alloy consists of a large number of short rod-shaped -MgZn2 precipitates, blocky -MgZn2 precipitates and granular precipitates. When the alloy is aged at 160 ℃ for 48 h, it consists of a large number of elongated precipitates and granular precipitates. The elongated precipitates are formed perpendicularly to the basal plane of magnesium. Compared to the Mg-8Zn-1Cu alloy, the sizes of elongated precipitates become much smaller