To investigate the thickening characteristics of ultrafine full tailings, the sedimentation test in measuring cylinder, the dynamic thickening test of small-scale and semi-industrial deep cone were carried out. The results show that the non-ionic flocculant with molecular weight of 12 million is the most beneficial to the settlement of tailings. With the increase of unit consumption of flocculant, the turbidity of overflow decreases and the underflow concentration is basically unchanged. With the increase of solid flux, the turbidity of overflow increases and the underflow concentration decreases. When the solid flux is 0.4t/m2·h-1, the feeding concentration is 12%, and the flocculant consumption is 50g/t, the average underflow concentration of the small-scale and semi-industrial dynamic thickening test is 62.8% and 74.4%, respectively. The sludge height has a significant influence on the underflow concentration. The underflow concentration increases as the DoseResp function with the increase of sludge height, which can be divided into three stages: slow growth (sludge height 1~4m), rapid growth (sludge height 4~7m) and basic stable (sludge height over 7~8m). This is related to the compression performance of tailings flocs at different sludge heights. According to the function relation between the underflow concentration and the sludge height, the sludge height can be adjusted to meet the required underflow concentration for production.