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Aptamer‐based probes are pivotal components in various sensing strategies, owing to their exceptional specificity and versatile programmable structure. Nevertheless, numerous aptamer‐based probes usually offer only a single function, limiting their capacity to meet the diverse requirements of multi‐faceted sensing systems. Here, we introduced supersandwich DNA probes (SSW‐DNA), designed and modified on the outer surface of nanochannels with hydrophobic inner walls, enabling dual functionality: qualitative detection for on‐site analysis and quantitative detection for precise analysis. The fragmented DNAs resulting from the target recognition, are subsequently identified through lateral flow assays, enabling robust on‐site qualitative detection of microcystin‐LR with an impressively low limit of detection (LOD) at 0.01 μg/L. Meanwhile, the nanochannels enable highly sensitive quantification of microcystin‐LR through the current analysis, achieving an exceptionally low LOD at 2.5×10−7 μg/L, with a broad dynamic range spanning from 1×10−6 to 1×102 μg/L. Furthermore, the process of target recognition introduces just a single potential error propagation, which reduces the overall risk of errors during the entire qualitative and quantitative detection process. This sensing strategy broadens the scope of applications for aptamer‐based composite probes, holding promising implications across diverse fields, such as medical diagnosis, food safety, and environmental protection. [ABSTRACT FROM AUTHOR]