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Major element, REE and oxygen isotopic compositions of fourteen clinopyroxene megacrysts from Nushan, eastern China have been obtained. They are believed to represent crystallization products of one mantle-derived alkali basaltic magma. Oxygen isotopic ratios are homogeneous within the same sample, but heterogeneous among different samples, 18O values of these megacrysts are from 4.86‰ to 6.48‰. We suggest that the oxygen isotopic variation of clinopyroxene megacrysts should be inherited from their source magma, and the heterogeneity of source magma results from contamination of subducted oceanic materials.