Due to the significant detrimental effects of nitroaromatic explosive on the environment and human health, sensitive, rapid, on-site and simple detection methods for explosives are in high demand. A novel label-free silicon quantum dots (SiQDs)-based sensor is designed for ultrasensitive detection of 2,4,6-trinitrotoluene (TNT) and 2,4,6-trinitrophenol (TNP). In this work, amino-functionalized SiQDs are obtained through treating the SiQDs with (3-aminopropyl)triethoxysilane (APTES). The amine-coated SiQDs are not only water-stable but also highly luminescent. Based on the dramatic and selective fluorescence quenching of the amine-coated SiQDs due to charge transfer that resulting from the formation of stable Meisenheimer complexes between electron-deficient TNT/TNP and electron-rich primary amine on the surface of SiQDs, an instant and sensitive sensor is developed for the detection of TNT/TNP which is able to not only directly suppress the fluorescent emission intensity of SiQDs but also induce SiQDs aggregation to result in self-quenching of SiQDs. The results reveal that the developed sensor has high sensitivity for the detection of TNT/TNP. As indicated in experimental results, the fluorescence intensity is proportional to the concentration of TNT/TNP. Meanwhile, linear correlations are obtained respectively for the fluorescence signals to the logarithmic TNT and TNP concentration with 6 and 7 order of range and the detection limit of TNT and TNP is 50 pg/mL for TNT and 5 pg/mL for TNP. Further experiments demonstrate that this analytical method is not susceptible to pH and prevent interference from other nitroaromatics or cationic ions. This simple and cost-effective sensor can be used to detect ultra-trace TNT/TNP in groundwater or seawater. Additionally, this sensor strategy may provide a convenient, rapid, highly sensitive and selective assay platform for nitroaromatic explosive.