Abstract: With the long-term high-intensity development and the increase of mining depth,the quality of raw coal of Shendong mining area deteriorates gradually,and the sulfur content of commercial coal also increases gradually.Based on the above,the representative raw coal of Shendong mining area was selected as the research object.The grain size distribution,density distribution rule and the embedded structure of sulfur-bearing minerals of the raw coal,including total sulfur and morphological sulfur were comprehensively analyzed by screening,floating and sinking,and scanning electron microscope.The suggestions for the coal preparation plant to further improve the production process were put forward.The main conclusions are as follows.The results show that the gangue in the selected raw coal of Shendong mining area is brittle,and more fine particles are enriched in the mining process,resulting in a higher ash and sulfur content of fine particles in the raw coal.The ash content of < 0.5 mm partial fraction is more than 5 percentage points higher than other grain levels,and the sulfur content also reaches more than 0.7%.Lump coal of >13 mm grain size accountes for 52.13%,the ash content is lower than other grain size and the sulfur content increases significantly. On the whole,with the increase of floating and settling density,the total sulfur content of raw coal increases slowly at first,and then increases rapidly after exceeding 1.6 g/cm3.When the floating and settling density is consistent,the total sulfur content of coarse particles is higher than that of fine particles on the whole.While the sulfur content of coarse particles in the range of >1.8 g/cm3 is lower than that of fine particles,indicating that with the decrease of raw coal particle size,the degree of dissociation of sulfur-bearing minerals gradually increases,and the inorganic minerals concentrate to high-density materials. The sulfur content of raw coal in Shendong mining area is mainly pyrite sulfur,accounting for more than 60%,followed by organic sulfur. In low density,organic sulfur is the dominant sulfur content,while in high density,pyrite sulfur is the dominant sulfur content. Pyrite sulfur is mainly distributed in the form of veins and grains,and the disseminated particle size is about 0.1 mm. In the subsequent production,the coal preparation plant should further reduce the selected upper limit according to the actual situation and realize the sulfur in the raw coal mineral fully disintegrate.At the same time,it should be actively to develop the selective removal of fine material into the desulfurization techniques such as magnetic separation,fine classification desliming technology.Meanwhile,the online detection technology of sulfur content should be strengthened to guarantee the quality of coal.