Abstract: The Xinchang composite igneous complexes include several composite lava flows and composite intrusive massifs.The composite lava flows consist of basalt and rhyolites/rhyolitic ignimbrite, and may accommodate partly a small amount of intermediate lavas and enclaves. The composite intrusive massifs consist of diabase and granite, and contain dioritic enclaves. Geochemically, these rocks are of calc-alkaline series, enriched in LREE, LILE (e.g. K, Rb and Ba), but depleted in HFS elements (e.g. Ta, Nb, Zr and Hf), and with similar REE patterns and trace elements spidergrams. They have limited range of ISr values from 0.7069 to 0.7079 and εNd(t ) values from -2.3 to -5.3, implying that a full exchange of trace elements and isotopic compositions took place among them. The overall elemental and Sr-Nd isotopic characteristics of the Xinchang composite igneous complexes are similar to those of the basalt-rhyolite composite lava flows and intrusions in the coastal area of Zhejiang and Fujian provinces.It is proposed that the Xinchang composite igneous complexes were formed under a extension tectonic setting and derived from the basaltic magma produced by partial melting of sub-continental lithospheric mantle which could have been influenced by early subduction processes, and underplated and interacted with deep crust melted granitic magma. This research, based on the composite igneous complexes, provides a typical case to better understand the evolution of Late Mesozoic geodynamic environmentand tectono-magmatic activities in the coastal area of southeastern China.