Abstract: Smoke density test of low smoke halogen-free cables is one of the important indicators for feedback on the combustion performance of cables. Based on IEC 60840:2020 (5.0 edition) and IEC 62067:2022 (3.0 edition), performance indicators of low smoke halogen-free flame-retardant sheathing materials for high voltage cables containing 36 ~500 kV were decomposed. Through experimental process and calculation principle of smoke density in IEC 61034-2:2005/AMD1:2013 and IEC 61034-2:2019 (3.2 edition), performance indicators that met the requirements under two calculation formulas were summarized and analyzed. The minimum transmittance critical value of high voltage cables met the requirements with different outer diameters was also analyzed to determine their variation trend and the scope of indicators, which could improve quality control of finished cable.