Quaternary Mg-Zn-Y-Ce quasi-crystal-containing alloys were fabricated using a metal mold casting route. The microstructures of Mg-Zn-Y-Ce alloys and the distribution of the major elements were analyzed. The differences in morphology and micro-hardness between quaternary Mg-Zn-Y-Ce quasi-crystals and ternary Mg- Zn-Y quasi-crystals were discussed. The result showed that the micro-hardness of Mg-Zn-Y-Ce quasi-crystals reached peak value when the content of Ce was 0.8at.%. Subsequently, various contents of Mg-Zn-Y-0.8Ce alloys were used to strengthen AZ91 magnesium alloys. The microstructural modification and mechanical properties of reinforced AZ91 alloys with and without solution, as well as their aging treatments, were also studied. Further research showed that aging-treated AZ91-10wt.%(Mg-Zn-Y-0.8at.%Ce) alloys exhibited excellent mechanical properties: their Brinell hardness, tensile strength, and elongation were HV91, 252 MPa, and 4.1%, respectively. Through this study, the range of application of AZ91 alloys can further be extended. Quaternary Mg-Zn-Y-Ce quasi-crystal-containing alloys were fabricated using a metal mold casting route. The microstructures of Mg-Zn-Y-Ce alloys and the distribution of the major elements were analyzed. The differences in morphology and micro -hardness between quaternary Mg-Zn-Y-Ce quasi-crystals and ternary Mg- Zn-Y quasi-crystals were discussed. The result showed that the micro-hardness of Mg-Zn-Y-Ce quasi-crystals reached peak value when The content of Ce was 0.8at.%. Successfully, various contents of Mg-Zn-Y-0.8Ce alloys were used to strengthen AZ91 magnesium alloys. The microstructural modification and mechanical properties of reinforced AZ91 alloys with and without solution, as well as Further aging-treated AZ91-10wt.% (Mg-Zn-Y-0.8at.% Ce) complexes showed excellent mechanical properties: their Brinell hardness, tensile strength, and elongation were HV91 , 252 MPa, and 4.1%, respectively. Through this study, the range of application of AZ91 alloys can further be extended.