With DSC, OM, XRD, SEM, TEM, Vickers hardness tester, and universal testing machine, the evolution of the microstructure and mechanical properties of Mg-6Zn-3Sn alloy during homogenization was studied, the reason for overburning and diffusion kinetics of the alloy were analyzed, and the homogenization scheme was determined. The results show that the decomposition of the Mg₂Zn₃ phase, accompanied by the precipitation of the Mg₂Sn phase, occurs after the single-stage homogenization. When the homogenization temperature increases to 350 °C, the Mg₂Zn₃ phase leads to overburning. The suitable homogenization scheme for the alloy is (335 °C, 24 h) + (400 °C, 6 h). During the double-stage homogenization, the hardness of the alloy decreases continuously and the mechanical properties show an increase first and then decrease, which is related to the solid solution of Zn and Sn atoms and the precipitation of the Mg₂Sn phase.