Abstract: The ultrabasic rocks of Mesozoie-Caenozoic era have been found in the northeastern Jiangxi Province They are mainly 1imburgite and breccia-like 1imburgite and intruded the Cretaceous red basins. The breccia-like 1imburgite is pipe shaped. The results of petrochemical Analyses indicate that these ultrabasic rocks contain 38.19～44.28% Si02，2.01～2.93% K20+Na2O，7.67～11.10% MgO，8.25-12.67% CaO and 11.94-14.51% Al2O3 etc. These ultrabasic rocks aye quite similar to the typical limburgite in chemical composition. The discovery of Mesomic-Caenomic ultrabasic rocks provides an important information for reevaluation of the perspective for the diamond prospecting in the northeastern Jiangxi Province.