Magnesium alloy are extensively used in aerospace and automobile industries due to their lowest density and superior mechanical properties, better corrosion and wear, low thermal coefficient of expansion as compared to conventional metal and alloy. The use of pure magnesium is rare due to its instability at high temperature and it is extremely corrosive in wet environment. Therefore use of magnesium alloys in aerospace and automotive transmission casting parts is critical. The better mechanical properties of these alloy and moderately low production cost make them a very attractive candidate for a variety of application both from scientific and technological point of view. The aim involved in cast alloy is to combine the desirable attributes of metal and rare earth element (REM), Lanthanum. Present work is focused on the study of behavior of Mg-Al-Zn alloy with different percentage of lanthanum produced by the stir casting technique. The microstructure and mechanical properties are investigated on the developed alloys. Microstructures are investigated by optical microscopy phases and the alloy compositions were identified by X-ray diffraction (XRD) and Scanning electron microscope.