Mafic dyke is the product of lithospheric spreading and crustal extension, which is of great significance for studying the nature of the mantle and the evolution of continental dynamics. Abundant and widely distributed mafic dykes are commonly and universally interpreted to be a manifestation of extensional tectonism. In the northern Guangdong Province of the Nanling Mountain, the Xiazhuang uranium deposits are considered as one of the largest granite-related uranium ore field in China. Mesozoic mafic dykes are widespread and regularly developed, which are closely associated with granite-related uranium deposits in the Xiazhuang uranium ore field. The geochronology and geochemistry of these mafic dykes and uranium deposits have been extensively studied. However, the link between mafic dykes and uranium mineralization are considerable controversy. The new Ar-Ar dating of the hornblende of the diabase, dioritic porphyrite and diabase porphyrite from the Xiazhuang uranium ore field yields the plateau ages of 200 similar to 190Ma, 179. 6 +/- 2. 8Ma and 145. 1 +/- 12. 1Ma, respectively. These results coupled with published geochronological data show that at least three major episodes of mafic dykes occurred in the study area at 200 similar to 190Ma, 180Ma and 145 similar to 140Ma, indicating that South China Block probably occurs the wide extension at 200 similar to 190Ma and 145 similar to 140Ma. The identification of mafic dykes at 200 similar to 190Ma in the northern Guangdong Province of the Nanling metallogenic province represents the extensional tectonism in South China block, which have been started at 200 similar to 190Ma after the Indosinian orogeny. Based on the fact that closely spatial and temporal relationships between uranium ore body and mafic dykes in the Xiazhuang uranium ore field, age gap between ore-forming and emplacement of mafic dykes is key to evaluate the role of mafic dyke in uranium mineralization. When the ore-forming event is slightly younger than the occurrence of mafic dykes, it is considered that magmatic activities represented by mafic dykes could not only supply mantle-derived CO2 ( noble gas He), which is indispensable for uranium mineralization, but also provide a favorable reducing environment to promote the deposition and enrichment of uranium from hydrothermal fluids. Accordingly, the emplacement of mafic dykes is much older than age of uranium mineralization, mafic dykes associated with deep faults could be still favorable factors for uranium deposition and fluid migration. Therefore, this paper reevaluates the role of mafic dyke in uranium mineralization, and provides some reliable suggestions for further prospecting in the Xiazhuang uranium ore filed and other similar deposits in the region which may have formed in a similar model.