<p>Zearalenone (ZEN) is a common contaminant in crops with serious food safety implications. By leveraging the etching effect of H₂O₂ on gold nanorods (Au NRs) and the catalysis of Fenton reaction, we have successfully developed two enzyme-linked immunosorbent assay (ELISA) kits with distinct principles. ZEN can be accurately quantified by both methods by measuring changes in the longitudinal surface plasmon resonance (LSPR) absorption peaks of Au NRs. Direct detection kit is simpler and faster, with a linear range of 0.2–4000 ng/mL, while indirect competitive kit is more complex and has a narrower linear range of 0.02–10 ng/mL. This study is expected to provide an effective analytical strategy for rapid screening and accurate monitoring of mold contaminants in food and agricultural products. </p><p>In this study, a novel dual-mode ELISA system was developed for the detection of zearalenone (ZEN) using Au NRs and their longitudinal surface plasmon resonance (LSPR) properties. By integrating H₂O₂-mediated nano-etching and Fenton reaction catalysis, the system enables both direct (0.2–4000 ng/mL) and indirect competitive (0.02–10 ng/mL) detection modes. The main work includes: (1) replacing the traditional enzyme colorimetric signal with an LSPR shift for accurate UV-visible quantification and visual multicolor readout; (2) optimizing the nanoenzyme catalytic system for improved reaction sensitivity; (3) eliminating the need for enzyme-labeled secondary antibodies in direct mode, thereby reducing cost and improving stability. The system was validated on grain samples with recoveries of 93.1-107.1% and detection limits of 0.2 ng/mL (direct) and 0.02 ng/mL (indirect). The modular design of the method allows it to be used for the detection of other mycotoxins (e.g., aflatoxin, ochratoxin) and offers great potential for food safety screening, agricultural monitoring, and environmental assessment. This work provides a cost-effective, sensitive and versatile platform for mycotoxin analysis.</p>