Abstract: The mineral composition of a copper-molybdenum mixed concentrate is complex in Heilongjiang Province. The content of −30 μm particles in the ore sample accounts for 45.56%, and the content of fine particles is high. The complex composition and high content of fine particles make the sedimentation operation of the concentrate thickener face a huge challenge of slow settling and high overflow turbidity. To investigate the flocculation and settling performance and related mechanisms of the ore, this paper first conducts single-factor flocculation and settling tests on the sample, examining the effects of flocculant molecular weight, flocculant concentration, flocculant unit consumption, slurry concentration, and slurry pH value on its flocculation and settling behaviour using settling height and supernatant turbidity as indicators; furthermore, the sediment products are analyzed by Fourier Transform Infrared Spectroscopy to explore the adsorption mechanism between mineral particles and flocculants; finally, molecular dynamics simulation results are used to analyze the interaction between various minerals in the sample and flocculant molecules and water molecules. The physical results show that the optimal flocculation and settling effect of the sample is achieved when the anionic polyacrylamide （APAM） has a molecular weight of 10 million, a preparation concentration of 1.60‰, a unit consumption of 25 g/t, a slurry concentration of 25%, and a slurry pH=11; the infrared spectroscopy analysis indicates that hydrogen bonding and chemical adsorption occur between APAM and the mineral surface; the molecular dynamics results reveal that the flocculation adsorption of APAM on the four main minerals is a spontaneous process, and the APAM molecules are closely distributed on the surfaces of the four minerals, while water molecules mainly distribute on the surfaces of chalcopyrite and molybdenite. The research results can provide a scientific basis for the flocculation and settling process of fine particles copper-molybdenum mixed concentrate and the design and development of new flocculant molecules.