Abstract: In view of the present ochratoxin A (OTA) method in the problems of complex and time-consuming process, a new quantitative OTA detection method based on the combination of weak magnetic signal detection technology and immunoassay technology was proposed. By modifying the surface of magnetic nanoparticles (MNPs) with OTA antibodies, a magnetic bead antibody complex with immune activity can be obtained.Under a magnetic field of uniform intensity generated by the Helmholtz coil, a magnetometer was used to detect the weak magnetic signal generated by the MNPs on the test line(T line) and the quality control line(C line) on the magnetic chromatography papers, and the ratio of the T:C line response magnetic signal, namely T/C value, was extracted. Through analyzing the T/C values with OTA concentration, a standardization curve can be obtained. The results showed that the detection results of MNPs response signal were basically consistent with the simulation results of linear magnetic dipole model, and a good linear correlation between OTA mass concentration and magnetic signal was obtained. The limit of the qualitative detection of the test strip was 0.10 ng/mL, the quantitative detection limit was 0.32 ng/mL, and the linear detection was 0.32-5 ng/mL.Thirty seconds were enough for completing a single test. This detection method can be used for real-time detection in the field and has a good application prospect.