The megacrysts discussed in this paper occur in Cenozoic alkali basalts of Jiangsu-Shandong-Anhui area. Garnet megacrysts belong to pyrope-almandine series, while monoclinic pyroxene megacrysts are of aluminous augites. Both megacrysts were formed through early crystallization of basaltic magma at high pressure. In contrast, the anorthoclase megacrysts seem to be of a relatively low pressure phase.Seven megacryst samples were analyzed for REE. The garnet megacrysts are characteristically rich in HREE, and the chondrite-normalized patterns show that (La/Yb)N ratio and (Ce/Yb)N are respectively 0.01-0.02 and 0.03-0.08. Fractional crystallization of the garnets caused HREE depletion in the melt. The augite megacrysts contain higher MREE, lower LREE and lowest HREE, with (La/Yb)_N ratio and (Ce/Yb)N being respectively 3-16 and 4-27. The augites led to MREE depletion and LREE enrichment in the basaltic magma. The anorthoclase megacrysts show relatively high positive Eu anomalies, Eu/Eu ratio being 4-7. Their crystallization gave rise to slight, negative Eu anomalies in the melt. The patterns of megacryst/melt REE partition coefficients are consistent with chondrite-normalized REE patterns of megacrysts.It can be concluded from the above discussion that REE distribution patterns of LREE enrichment and HREE depletion in alkali basalts are caused jointly by degree of partial melting, fractional crystallization of megacrysts and differentiation of basaltic magma.