In order to find out the main causes of copper loss in copper ore dressing process,the mineral composition,dissociation degree,continuity degree and embedding state of minerals in copper tailings are researched by means of advanced scanning electron microscopy,energy spectrum and BPMA analysis system.The results show that the copper minerals in the copper tailings are mostly chalcopyrite and covellite,and the copper distribution rates are 89.01 % and 10.99 % respectively; the grain of the copper minerals is tiny in microfine particles with both the grain size smaller than 38 μm;the monomer dissociation degree is low for chalcopyrite and it is closely associated with gangue minerals while covellite is mostly in monomer form.The process mineralogy research results provides theoretical basis for the optimization of copper ore dressing process and the improvement of recovery rate.