Abstract: The knowledge of core material of polymetallic nodules is of great importance for clarification of the distribution and origin of nodules in ocean. Based on dissection of about 178 pieces of samples of polymetallic nodules obtained from the Fast Pacific Basin by investigation ship “HAIYANG 4” of MGMR among which 53 pieces are basalt-nuclei in composition, accounting for 29.8%, this paper comprehensively studied and analyzed the features of these basal-nuclei of nodules, including lithology, petrochemsitry, mineral constituents, trace-element geochemistry and isotope chronostratigraphy, etc. The authors come to a conclusion that the basalt-nuclei of nodules belong to ocean island tholeiite or alkali-basalt. There are of calc-alkaline series and alkali series, which include olivine, tholeiite, and alkali basalt, and they were mainly formed in the Tertiary. In the light of studies of the or in of basalt-nuclei of nodules, and analysis of the relationship between the basalt-nuclei and the distribution of ploymetallic nodules, the authors pointed out that basalt-nuclei of nodules are derived from seamount basalt in the study area. It is found that seamount basal mainly effected and control1ed the formation and distribution of polymeta11ic nodules, which provied enormous nuclei.