Abstract: In order to improve the separation effect of the 0.5~0 mm separation system of Meishan preselection tailings washing ore，aiming at the problems of large fluctuation of process index in this process， the technical transformation is carried out on the site，the uniform feeding of concentrated large wells is optimized and adjusted，the expansion of low intensity magnetic separation tank is reformed，the low intensity magnetic flushing water is optimized，and the magnetic declination is adjusted to solve the feeding uniformi⁃ ty of LGS-1750 vertical ring pulsating high gradient magnetic separator. The optimized analysis results show that the concentrated well has the effect of iron extraction，desliming and silicon reduction in the process of concentration and settlement. The TFe grade of the low intensity magnetic separation concentrate is 62.01%，the TFe grade of the tailings is 15.91%，and the low intensity magnetic concentrate yield is 15.59%. After low intensity magnetic separation and high intensity magnetic separation，the comprehensive concentrate TFe grade is 49.36%，the yield is 28.21%，the recovery rate is 63.15%，and the total wet tailings iron grade of gravity separation is reduced to 12.55%. The low intensity magnetic and high intensity magnetic process system has remarkable effect on treating all slime in gravity separation.

Key words: preconcentration ore washing, fine fraction, tailings, concentrate, magnetic separation