Abstract: The self-made small inverter electroslag furnace was used to carry out electroslag remelting experiments on binary slag system (30% Al₂O₃+70% CaF₂) and ternary slag system (20% Al₂O₃+20% CaO+60% CaF₂) under the mode of DC power supply. The oxygen and nitrogen content and the quantity, size, distribution and morphology of inclusions in electroslag ingots were analyzed by using oxygen and nitrogen analyser and ASPEX automatic inclusions analysis system to explore the influence of slag composition on the cleanliness of electroslag remelting ingots under DC power supply mode. The results show that in the same power supply mode (DC positive or DC reverse), the stability of the slag system is the main influencing factor on in the oxygen content, the number and distribution of inclusions of electroslag ingot, but has little effect on the nitrogen content and morphology of inclusions. Compared with the binary slag system, the number of inclusions in the ternary slag system remelted ingot is significantly reduced, and their size is reduced, and their distribution is more dispersed, this is because the stability of CaO is stronger than that of Al₂O₃. In the same slag system, the number of inclusions in the electroslag ingot prepared by DC positive connection is significantly higher than that of DC reverse connection, and there is no obvious difference in the morphology of inclusions. The electrolysis of oxides in the slag cell is higher than that of DC reverse connection, and the calcium content of inclusions in the electroslag ingot prepared by DC positive connection is lower than that of DC reverse connection.