Abstract: The resource utilization of coal gasification slag has become a research focus in the field of coal-based solid waste. The physical and chemical characteristics and the heavy metal migration rules of coal gasification slag are very important for its resource utilization. Firstly, three coal gasification technologies of entrained flow, fluidized-bed and fixed-bed gasification were introduced and compared. Then, the physical and chemical characteristic of coal gasification slag, including particle size composition, apparent and microscopic morphology, inorganic and crystalline mineral composition and carbon residue content, were summarized. Finally, the migration behavior, risk assessment code and leaching behavior of heavy metals in coal gasification slag were analyzed. The physical and chemical characteristics of coarse slag and fine slag are different to some extent. From the perspective of physical and chemical characteristics, the differences of fine slag and coarse slag are as follows. The particle size of fine slag is much lower than that of coarse slag, about 60% of fine slag is less than 0.250 mm, and about 50% of coarse slag is more than 0.500 mm. The specific surface area of fine slag is larger than that of coarse slag, and the average pore diameter is smaller than that of coarse slag. The inorganic components of coarse slag and fine slag are mainly SiO₂, Al₂O₃, CaO and Fe₂O₃, in which the acid oxides account for about 35%−80% of the total components, the basic oxides account for about 20%−65% of the total components, and the coarse slag has more basic oxides, and the fine slag has more acidic oxides. The crystalline minerals and amorphous substances in coarse slag and fine slag are not simple coal gasification residues, but formed after a series of complex physical and chemical reactions in the gasification process. Both of the main crystalline minerals of coarse slag and fine slag are quartz, calcite and mullite, but the types and contents of other crystalline minerals are very different, which is mainly affected by factors such as coal type and gasification temperature. The carbon residue content of coarse slag is mostly 3%−20%, while that of fine slag is mostly 20%−40%. The carbon residue content of coarse slag is lower than that of fine slag, but the reactivity of coarse slag is higher than that of fine slag. The distribution of carbon residue content in coarse slag or fine slag with different particle sizes is uneven. The medium coarse slag with about 0.250 mm has a higher carbon residue content, while the highest carbon residue content in fine slag corresponds to the particle size of about 0.125−0.250 mm or large particle size, and the carbon residue content in fine slag increases with the increase of particle size. The residual carbon in the gasification slag has a porous structure with more large pores and good connectivity. The residual carbon in the gasification coarse slag is mostly amorphous, while the residual carbon in the gasification fine slag has obvious aromatic structure and more aromatic C—C or C—H bonds. In terms of heavy metal migration, there are different degrees of heavy metal enrichment in coarse slag and fine slag, and the enrichment factors are closely related to the volatility of heavy metal elements. Compared with coarse slag, fine slag has greater environmental risk, and heavy metals such As Cd, Ni, Cu, Zn, AS, Co, Mo, Se, Pb and Cr in gasification slag have higher environmental risk, which should be paid more attention to. The leaching behavior of heavy metals in gasification slag is dependent on leaching scheme, leaching time and particle size of gasification slag. Under strong acid or/and strong alkali conditions, most heavy metals will have higher leaching concentration, and the leaching concentration of heavy metals increases with the increase of time until it becomes stable. Meanwhile, the leaching concentration of heavy metals in small-size gasification slag is usually higher than that in large-size gasification slag.