In the heavy medium coal preparation process, the magnetic field intensity of the traditional drum magnetic separator is low and the magnetic field attenuation speed is fast, and the effect of medium recovery is often not up to expectations. Taking the coal preparation plant of Tang 'an Coal Mine as an example, this paper analyzes the problem of large consumption of heavy medium during the operation of the magnetic separator in the coal preparation plant, and points out that the reason is that the magnetic field strength of the magnetic separator is insufficient, and decides to use the dry permanent magnet disk magnetic separator to replace the original drum magnetic separator. At the same time, the feeding mode, magnetic separation plate and unloading plate of the disk magnetic separator are optimized. The practice shows that the designed disk magnetic separator has a good application effect and solves the problem of heavy medium consumption in Tang 'an Coal Mine Coal Preparation Plant.