Through the study of lithology and LA-ICP-MS zircon U-Pb dating, the main invasion period of Hongshanzi rock and the age of intrusive rock formation were determined. It is clear that Hongshanzi rock is a complex rock. The authors discussed its geological significance. The study of petrography indicates that Hongshanzi complex rock is composed of middle coarse grained alkali feldspar granite, porphyritic biotite granite, finebiotite granite and granite porphyry. The LA-ICP-MS zircon U-Pb dating results show that the age is 153.6±1.2 Ma for middle coarse grained alkali feldspar granite, and 151.4±1.1 Ma for porphyritic biotite granite, which are in accordance with the data obtained around the ore-bearing volcanic basin, and belong to the early period of Late Jurassic. The age of finebiotite granite is 131.5±1.8 Ma and that of granite porphyry is 133.3±1.4 Ma, consistent with the age of the granite porphyry which invaded Hongshanzi Basin and belonging to the early period of Early Cretaceous. Therefore, Hongshanzi Yanshanian complex rock is composed of two different periods in Yanshanian epoch, whose time span is 20 Ma. Studies show that the Hongshanzi uranium ore deposit occurs along the contact zone of granite porphyry of early Early Cretaceous and volcanic rocks of Late Jurassic, which indicates that the contact zone between complex rock of middle coarse grained alkali feldspar granite, porphyritic biotite granite and fine biotite granite and granite porphyry is the best place for mineral exploration, and this conclusion was verified by the uranium ore exploration.