The Chinese largest gem quality corundum—sapphire deposits is located in Changle, Shandong Province. Changle corundum occurs as megacryst in the Cenozonic basalt, showing roundish shape and having sharp boundary contact with host basalt. The well developed reaction rim of Al-riched spinel and titanium magnetite, around corundum megacrysts indicate they are deep mantle derived xenocryst. The study of corundum megacryst and its reaction rim can reveal their genesis and evolution information. Methods:The petrography, electron microprobe and LA-ICP-MS (Laser Ablation-Inductively Coupled PlasmaMass Spectrometry) study methods are applied in this paper. Results:The major and trace mineral compositions, key elements such as Ga/Mg、Cr/Ga、Fe/Ti、Fe/Mg ratios of two groups samples of the corundum megacrysts (CL-1 and CL-2) indicate they are magmatic origin. In compared with the the CL-1 group samples, the CL-2 group samples of Changle corundum obviously overprint the features of late melt infiltration metasomatism. The reaction spinel rim diaplays transitional compsition characteristics from corundum megacryst to spinel megacryst, and the key element data of corundum and spinel megacrysts exhibit obvious affinity. Conclusions:The spinel megacryst is the product of corundum after complicated metasomatic evolution. In adation, Changle corundums present mineral chemical features of crystallization from alkali melt that most likely derive from low extraction of metasomatic enriched mantle rocks.