Via　the　solid　phase　reaction,　Mg-Al　spinel　has　been　synthesized　by　using　industrial　waste　slag　from　aluminum　factory,　basic　magnesium　carbonate　and　a　little　amount　of　clay　as　the　main　raw　materials.　The　influences　of　Cr　2O3　mineralizer　on　crystalline　structure,　micro-morphology　and　properties　of　synthesized　Mg-Al　spinel　are　discussed.　The　synthesized　product　was　characterized　by　using　XRD　and　SEM,　and　the　relative　contents　of　each　crystalline　phase　are　calculated　by　relevant　analytical　software　such　as　Philips　plus,　Rietveld　quantification　and　so　on.　The　experimental　results　show　that　a　certain　amount　of　Cr2O3　is　helpful　to　the　formation　of　Mg-Al　spinel,　and　when　the　addition　of　Cr2O3　is　2.0%,　Mg-Al　spinel　in　the　system　exists　in　the　form　of　solid　solution　(Mg　0.68Al0.32)(Al0.84Mg0.16)　2O4　whose　content　is　the　highest　reaching　91%.　Then　the　corresponding　indexes　of　each　property　are　as　follows:　water　absorption　3.0%,　apparent　porosity　9.8%,　bulk　density　3.36　g-cm-3,　and　flexural　strength　83.32　MPa.　Therefore,　we　can　confirm　that　the　optimum　addition　of　Cr2O3　mineralizer　is　2.0%.　1.