An integrated geochemical analysis has been made on mantle-derived hastingsite megacrysts, which are rare in the world. Their major element, REE and Sr and Nd isotope geochemical features indicate that the hastingsite megacrysts are the product of crystallization of alkali basaltic magma in the mantle. They are xenocrysts relative to their host-basalt. These megacrysts have no genetic relation with their coexisting peridotite inclusions, but are probably related to their coexisting black inclusions.