Abstract: Damingshan is an important area of tungsten metal resources in southern China. The Damingshan tungsten deposit was tied up with the Yanshanian magmatism activity. Samples of tungsten veins and muscovite were determined by 40Ar/39Ar fast neutron activation techniques. The plateau age of muscovite is 97.10±0.86 Ma, with normal and inverse isochron ages being 96.6±1.7Ma and 96.5±1.1 Ma. The age of the sample is reliable. According to the results of the 40Ar/39Ar dating, the time limit of tungsten mineralization should be 97Ma, which indicates that the ore-forming epoch of the Damingshan ore deposit is late Yanshanian. The large-scale mineralization in the Damingshan metallogenic belt of Guangxi might be attributed to the Mesozoic lithospheric extension in southern China.