Abstract: Mafic rocks from the eastern Lower Yangtze region， including Luzong ， Huaining ，Fanchang，Tongling and Ningwu areas，belong to alkaline series and are characterised by high U and Th concentrations(averaging 2.90 and 10.01 x 10-6)and with average Th／Pb and U／Pb ratios of 0.635 and 0.184，respectively．The least contaminated samples show initial Pb isotopic ratios of 206Pb/204 Pb= 17. 65～ 18.60，207Pb／204Pb= 15.42～ 15.50 and 208pb／204Pb=37.67～38.04．The initial basaltic magma came from the enriched lithospheric mantle．which is dominated by EM II component，and subordinated by EM I component．Since the Pb isotopic ratios of the studied rocks are lower than those of basalts from southwestern Dabie and western part of the Lower Yangtze region，but the U／Pb and Th/Pb ratios of the studied mafic rocks are higher than those of the latter region，it is inferred that the Mesozoic lithoshperic mantle beneath the eastern Lower Yangtze region suffered metasomatism by fluid from subducted slab．EM I-type enriched mantle is commonly observed in the North China block。and EM II-type isotope signature appears to dominate the South China bloc k in the late Mesozoic Era．This was closely related to deep subduction of Yangtze block in the Triassic time．Although the Cenozoic basalts from eastern China show depleted characteristics because of large scale lithospheric thinning ，the residue of Mesozoic lithospheric mantle is still kept in the Cenozoic mantle，shown by their Pb isotope signature．