8-Hydroxydeoxyguanosine (8-OHdG) is one of the main products of DNA oxidative stress injury and has been widely used for quantitative analyzing ROS levels. However, the intracellular detection of 8-OHdG is rarely reported and could provide for a novel tool for oxidative damage research. Here, a highly fluorescent silver nanocluster was synthesized by conjugating 12 cytosine bases as Ag nanocluster templates with 8-OHdG aptamer as the specific binding target (named 8-OHdG-12C), resulting in a 10-fold increase in fluorescence intensity of the as synthesized probe. The 8-OHdG-12C@AgNCs showed a good fluorescence property and were stable for weeks. In addition, it can visualize intracellular 8-OHdG in a spatiotemporal manner. We used oxidative or reductive inducers of ROS and showed that the probe was located within cells and proportional to the cell oxidative damage induced. Together, these results indicate that 8-OHdG-12C@AgNCs hold great potential for in vivo 8-OHdG detection and may be a useful method to determine how DNA oxidative damage influences cancer cells and apoptosis.