Aegirite is a gangue mineral often associated with iron ore. Due to its low hardness, it is easier to be crushed and argillated than iron ore in the grinding process. The argillated fine aegirite further increases the difficulty of iron tailings treatment. In this study, the effects of 6 kinds of diamines with different molecular chain lengths and both ends were amino on the flocculation performance of aegirite were explored through flocculation sedimentation test, and 1,8-octamethylene diamine (ODM) with the best flocculation effect was selected through free sedimentation test, flocculant type test, pH test and flocculant concentration test in sequence. The adsorption mechanism of ODM on the surface of fluorite was investigated using Zeta potential measurements, Fourier-transform infrared spectroscopy (FTIR), and X-ray photoelectron spectroscopy (XPS) analysis. The results of flocculation and sedimentation test showed that the best flocculation effect of ODM on aegirite was achieved when pH=6 and ODM concentration was 0.1wt%. In this case, aegirite settles completely within 60 s, and the rate of flocculation settlement is about 4 times that of free settlement. In addition, the Zeta potential of aegirite before and after the flocculation reaction was measured by the mechanism test. After adding the flocculant, the zero potential point of aegirite moved from 4.56 to 6.56, indicating that the interaction between the flocculant and the surface of aegirite was obvious. The adsorption behavior of the flocculant on the surface of aegirite was verified by FTIR analysis, and the functional groups belonging to the flocculant were adsorbed on the surface of aegirite. The adsorption mechanism was verified by XPS. It was found that the high resolution spectra of C 1s and N 1s after the treatment of the agent showed obvious new peaks, which further indicated that the agent was adsorbed on the surface of aegirite, and the binding energy of the upper peak of the Fe 2p spectrum was shifted by 0.1 eV, indicating that the adsorption behavior was non-chemisorption. The mechanism test results showed that ODM acts on the surface of aegirite mainly through electrostatic adsorption and hydrogen bond adsorption, and electrostatic adsorption played a dominant role in the adsorption process.