Helium isotope compositions of the mantle xenoliths and megacrysts in the Cenozoic basalts in the eastern China were measured. The samples were collected from Ludao of Heilong-jiang, Huinan and Jiaohe of Jilin, Kuandian of Liaoning, Hannuoba of Hebei, Nushan of Anhui, Dingan of Hainan. The 3He/4He ratios of the mantle xenoliths and megacrysts from the most areas were about 1×10-5, and were similar to those of the MORB, thus reflecting the characteristics of the MORB-typed depleted mantle. The 3He/4He ratios of the mantle xenoliths from Jiaohe were 4.8 ×10-6 and the 3He/4He ratios of xenoliths from Hannuoba vary from 0.15×10-6 to 7.4×10-6, obviously lower than those of the MORB, and even lower than the atmospheric helium isotope ratios, indicating that the continental mantle was strongly replaced in Jiaohe and Hannuoba areas. The helium isotope compositions of the mantle xenoliths and megacrysts in the same region vary in a very wide range. It is inferred that the mantle xenoliths and megacrysts were Helium isotope compositions of the mantle xenoliths and megacrysts in the Cenozoic basalts in the eastern China were measured. The samples were collected from Ludao of Heilong-jiang, Huinan and Jiaohe of Jilin, Kuandian of Liaoning, Hannuoba of Hebei, Nushan of Anhui, Dingan of Hainan. The 3He / 4He ratios of the mantle xenoliths and megacrysts from the most areas were about 1 × 10-5, and were similar to those of the MORB, thus reflecting the characteristics of the MORB-typed depleted mantle. The 3He / 4He ratios of the mantle xenoliths from Jiaohe were 4.8 × 10-6 and the 3He / 4He ratios of xenoliths from Hannuoba vary from 0.15 × 10-6 to 7.4 × 10-6, obviously lower than those of the MORB, and even lower than the atmospheric helium isotope ratios, indicating that the continental mantle was strongly replaced in Jiaohe and Hannuoba areas. The helium isotope compositions of the mantle xenoliths and megacrysts in the same region vary in a very wide range. It is inferred that the mantle xenoliths a nd megacrysts were