Mg92Zn4Y4 and Mg92Zn4Y3Gd1 alloys with long period stacking ordered (LPSO) structure phases were prepared by conventional solidification process. By OM, SEM, EDS, XRD and TEM analysis the phases and 14H-LPSO structures of the two alloys were characterized. The results show that as-cast Mg-alloy with the atomic ratio of Zn/RE = 1 will lead to LPSO phase; adding of Gd element to Mg92Zn4Y4 alloy can facilitate the formation of LPSO phase, and its volume fraction increases from 12.1% to 30.4%; Mg dendrites are split and refined during the precipitation of LPSO phase formed at high temperature, resulting in that the average grain size of a-Mg decreases from 50 μm to 10 μm; the solidification microstructure of as-cast Mg92Zn4Y4 alloy is a-Mg solid solution + Mg12ZnY + Mg3Zn3Y2 + Mg-Y; In Mg92Zn4Y3Gd1 alloy, the as-cast microstructure is confirmed to be composed mainly of a-Mg solid solution, Mg12Zn(Y, Gd) and Mg3Zn3(Y, Gd)2; at room temperature, the compression ratio and the thermal conductivity of Mg92Zn4Y4 and Mg92Zn4Y3Gd1 alloys are 12.4% and 15.5%, and 99.233 W·(m·K)-1 and 88.639 W·(m·K)-1, respectively.