Abstract: The studied diabase sills are found in Xuzhou-Suzhou area o f the southeastern part of North China Plate.They intruded into the NeoProterozo ic strata and might be the products of two stages. Isotopic ages of the two-s tage diabase sills are 706-723 Ma and 604－654 Ma， respectively，corresponding to the early and late Sinian period. The sills are tabular and wedge-shaped ,with a thickness from tens to more than hundred metres.The emplacement depth o f the diabase sills ranges from 0.05km to 2km.They are hypabyssal to subsurfac e intrusives and were folded during the Mesozoic time together with their sur rounding rocks. 　　The sills are composed of diabase and quartz-diabase. A lithological change o ccurred in some thick sills.The olivine (hyalosiderite)-bearing diabase， amy gdaloidal diabase and medium-to coarse-grained diabase (sometimes alkali gabbr o) occur at the bottom， top and middle parts of the sills， respectively. Ch emical compositions of the sills are enriched in SiO2， CaO and depleted in Al 2O3， MgO， (K2O + Na2O). In the K2O-TiO2-P2O5 plot， all samp le points almost fall into the field of continental tholeiite. It is therefore deduced that the diabases might belong to the tholeiite-series occurring with in the North China Plate. 　　The chondrite-normalized REE patterns of diabases show a Eu smooth-type， an e nrichment in light REE and a small separation between LREE and HREE. The rock s are enriched in K， Rb， La and depleted in Nb, Sr.The depletion of Nb is almost a common feature for all continental tholeiite-series rocks. Spidergr am of Nb normalized ratios and Nb-Zr， Y-Zr related diagrams show that the basal tic magma， from which the diabase was crystallized， might be generated from t he transitional mantle. An excellent distribution of positive slope line for a ll sample points in the La/Sm vs. La diagram suggests that the rocks were mainl y generated by partial melting.The spidergram of Yb normalized ratios，the Thom pson diagrams of trace elements and the Nb* anomaly values calculated from ch ondrite-normalized Nb， K， La values show that the basic magma was contaminate d by the crustal or granitic materials during its upwelling.