The design of fluorescent probes for turn-on sensing of anions has been especially significant because it can effectively enhance sensing sensitivity by decreasing the background interference. In the present work, we have systematically studied the potential applications of fluorescent quantum dots (QDs) in turn-on anion sensing. The fluorescence of QDs are firstly quenched by three different mechanisms, i.e. fluorescence resonance energy transfer, electron transfer and surface states modulated fluorescence. The fluorescence of the pre-quenched QDs can then be recovered by various anions due to the modulating effects of added anions on the interaction between QDs and QDs, the interaction between QDs and quenchers, and the surface chemistry of the quenched QDs, respectively. The results described here indicate that turn-on sensing of various anions by QDs-based systems can be achieved by rationally choosing fluorescence modulating strategies, demonstrating the versatility of QDs in the corresponding applications.