A novel fluorescence strategy based on the outstanding catalytic capability of CuS nanoparticles (CuSNPs) has beendeveloped for highly sensitive and specific determination of o,o-dimethyl-o-2,2-dichlorovinyl phosphate (DDVP) under enzyme-free and hydrogen peroxide (H2O2)-free conditions. In the presence of DDVP, CuSNPs can catalyze non-fluorescence substratum of Amplex red (AR) into resorufin, which exhibits fluorescence emission at 584nm under excitation at 540nm. The sensing system exhibits outstanding specificity and only responds to DDVP and noother organophosphorus pesticides (OPs). A wide linear range is obtained from 0.0001 to 0.1μg/mL, and the limit of detection (LOD) is0.1ng/mL. Furthermore, paper-based test strips have beenconstructed for visual detection of DDVP under ultraviolet light irradiation. By integrating a smartphone installed with Color Picker APP, point-of-care detection with quantitative determination is realized, demonstrating substantial potential applications of the as-developed assay for in situ detection. Graphical abstract.