The Wangzhoushan caldera is located in Cangnan, southeastern Zhejiang, and the main eruption products are Late Cretaceous rhyolites and rhyolitic pyroclastic rocks. The central intrusive body in the caldera is the typical alkaline granite, containing typical alkaline ferromagnesian minerals such as arfvedsonite and aegirine, and develop micrographic texture and miarolitic structure. Methods: Based on the field work, we conducted mineralogy, petrology, zircon U- Pb geochronology, whole- rock geochemistry, whole- rock Nd isotope and zircon Hf isotope studies for the Wangzhoushan alkaline granite.Results: LA- ICP- MS zircon U- Pb dating results show that the crystallization ages of alkaline granites are 91.30±1.10~90.43±0.76 Ma. The alkaline granites have high SiO2contents (76.9%~77.9%), and alkalis contents (Na2O+K2O=7.80%~8.51%), and low CaO, MgO, Al2O3. They are rich in large ionic lithophile elements (LILE; e.g., Rb, K) and high field strength elements (HFSE; e.g., Nb, Ta, Zr, Hf), poor in Ba, Sr, P, Ti, and show high 10000Ga/Al values (3.82~4.28) and high zircon saturation temperature (798~889 ℃). Different samples of the Wangzhoushan alkaline granites have similar whole- rock Nd isotopic compositions \[εNd(t)= -4.2~-3.8\] and zircon Hf isotopic compositions \[εHf(t)= -6.4~-1.7\], indicating that the Wangzhoushan alkaline granites may be mainly derived by partial melting of crustal materials with minor contributions from mantle- derived components.Conclusion: The Wangzhoushan alkaline granites belong to the typical peralkaline A- type granite, which is another example found in the coastal areas of Zhejiang and Fujian Provinces. The magma generation of the Wangzhoushan alkaline granites and the contemporaneous coastal alkaline granites (101~86 Ma) in Zhejiang—Fujian is controlled by the subduction and rollback of the paleo- Pacific plate in the Late Cretaceous. Under the strong extensional tectonic setting, the depleted mantle- derived magma upwelled, resulting in the partial melting of the middle and lower crustal materials, and the magma of the high- silica peralkaline A- type granites were formed by the magma mixing and fractional crystallization processes.