An enhancement of the TL sensitivity at ~400 o C in granitic quartz with accumulated radiation dose is observed. Studies of dose-rate effects and HF etching suggest that alpha radiation is the dominated source for creating such enhancement. HF etching for 100min can remove the outer layer of quartz grains, irradiated by alpha particles from other minerals. The equivalent alpha dose from the radiation of the quartz grain itself can be deduced by extrapolating the growth curve of TL sensitivity against additive alpha dose. The age of quartz is obtainable when the annual alpha dose is properly estimated.