Aflatoxin B (AFB) is a potent carcinogen which threatens human health, therefore, rapid and efficient detection of AFB is highly needed. Herein, a novel turn-on ratiometric fluorescent nanoprobe (RhB@NH-MIL-53(Al)) was fabricated via a facial grinding for sensing AFB. With increasing AFB concentration, the fluorescence of Al-MOFs was enhanced due to molecular clamp action and electron transport, while the fluorescence of RhB remained almost unchanged, thus obtaining limit of detection (LOD) of 4.16 nM in the range of 0.005-2.56 µM. The sensor demonstrated excellent anti-interference capabilities and gave reasonable results when used to measure AFB in grains. In addition, a paper-based portable sensor for AFB detection was developed with a LOD of 29.89 nM in the range of 0.04-12.8 µM, while the colour changes from light pink to blue upon UV light exposure, making it a straightforward and effective technique for the on-site determination of AFB.