In order to explore petrogenesis of the early Cretaceous Hongzhen granite in Huaining County, Anqing City, Anhui Province, and further confirm geochemical characteristics of the magma source, as well as reveal the special basement structure in this area of close to the Tancheng—Lujiang Fault. Methods: Combined with field work and microscope observation, analysis of the SIMS zircon U- Pb isotopic dating, XRD major elements, ICP- MS trace elements, TIMS Sr—Nd—Pb isotopes, and LA- MC- ICPMS zircon Hf isotope are carried out. Results: The SIMS zircon U- Pb dating confirms that the Hongzhen granite was formed at 126.2±2.0 Ma. This granite has characteristics of high silicon and potassium, and is I- type granite, belonging to high potassium calc- alkaline series. It also shows enrichment of light rare earth elements and large ion lithophile elements, depletion of middle rare earth elements and high field strength elements. The Hongzhen granite has enriched Sr—Nd—Hf isotopic and low radiogenic Pb isotopic compositions , with 87Sr/86Sr(t) of 0.7065－0.7066, εNd(t) of -10.9－-12.0, zircon εHf(t) of -6.7－-13.2， 206Pb/204Pb(t) of 17.063－17.109, 207Pb/204Pb(t) of 15.568－15.57, and 208Pb/204Pb(t) of 37.351－37.373. Conclusions: The Hongzhen granite formed at 126.2±2.0 Ma, which is simultaneous with the A- type granites form the Middle—Lower Yangtze River region and the I- type granites from the Dabie Orogen. It was derived from hydrothermal partial melting of the Paleo—Mesoproterozoic sedimentary rock with middle—low degree of maturity, induced by underplating of mantle derived magma, and experienced fractionation of dominant amphibole. Concerning the magma source, the Hongzhen granite is similar to the homochronous granites from the Dabie Orogen, and quite different from the homochronous A- type granites in the Middle—Lower Yangtze River region, indicating that the upper and lower crusts beneath the Hongzhen area have different tectonic affinities. During early stage of early- Cretaceous, the west wall of the southern Tan- Lu Fault suffered strongly southward compression, which induced random flow of the lower crust of the Dabie Orogen. The flowed lower crust crossed the Tan- Lu Fault and entered into the lower crustal region beneath the Hongzhen area, which was the source of granite.