In this study, an ultrasensitive electrochemiluminescence (ECL) immunosensor was fabricated for a rapid determination of ochratoxin A (OTA) based on gold nanoparticles-hybridized mesoporous carbon (AuNPs@MC). The ECL immunosensor was constructed by modifying an anti-OTA–luminol–AuNPs@MC ionic liquid (IL) dispersion on glassy carbon electrodes. AuNPs@MC presented remarkable signal enhancement performance, and IL was adopted to increase the conductivity of the ECL immunosensor. The voltage was applied by a single-step cycle pulse method, which limited the continuous consumption of luminol and increased the stability of the ECL immunosensor. The proposed ECL immunosensor is simple, rapid, sensitive, specific, stable and reliable. Under optimum conditions, a wide detection range of 1 pg mL⁻¹ to 50 ng mL⁻¹ with a detection limit of 0.3 pg mL⁻¹ was achieved. The proposed ECL immunosensor exhibited great promise in the food analysis field.