Qibaoshan is a Mesozoic volcanic apparatus located tectonically in the joint area among the Jiaonan uplift, Jiaolai depression and Yishu deep fault zon e. T he pyroxenemonzonite studied in this paper is the main rock type of the centra l stock of Qibaoshan caldera. Chemically, these rocks are rich in alkali, especia lly in potash (K2O+Na2O = 7.60%~9.71% and K2O/Na2O = 0.99~1.45), and have hi gh aluminum contents and relatively low titanium abundance. They are also rich i n LILE, but poor in siderophile elements, and have high Rb/Sr, K/Nb, Th/Nb and Ba/Nb ratios. Their ΣREE values and LREE/HREE ratios are obviously high, which range from 444.3×10-6 to 810.6×10-6 and 28.52~33.80 respe ctively. These rocks have high ISr ratios and quite low εNd(t) values (I