Aiming at the difficulty to satisfy the large flow rate and high sensitivity of the online wear detection system for mechanical instruments simultaneously， a multi-channel online wear particle detection sensor structure based on oppositely arranged ring magnets is proposed. By establishing the mathematical model of the magnetic properties of the sensor and the magnetization of ferromagnetic wear particles， the analytical solution of the magnetic perturbation， is derived when the wear particles pass through the sensor . Then， the influence law ofsensor structure parameters on the sensor performance is verified through simulation and experiment. The research results show that the magnetic flux density in a ferromagnetic spherical wear particle passing through the sensor is about three times the background magnetic induction intensity， and the sensitivity of the sensor， when the induction coil is arranged at the outer edge of the magnet， is about 10.1% higher than that the coil is arranged at the inner edge of the magnet. In addition， with the increase of the outer diameter of the magnet and the distance between the two magnets， the induction voltage output by the sensor shows a trend of increasing first and then decreasing， and the sensor with optimized structural parameters can effectively detect the ferromagnetic wear particles with a diameter of 80 μm.