Abstract: Ultra-pure anthracite can undergo the modifications of its structure and ash composition via vacuum heat treatment, which improves its electroconductivity and further enhances the electrical properties of conductive materials prepared from it. Characterization methods including Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) are employed to analyze the evolution of structure and ash composition of ultra-pure anthracite during vacuum heat treatment, and to investigate the variation law of anthracite's electroconductivity throughout the process. Results show that when the ultra-pure anthracite is tested from 300 ℃ to 1 200 ℃, part of the carboxyl and carbonyl groups are removed, most naphthenes gradually undergo aromatization, the condensation degree of aromatic hydrocarbons increases, then the electroconductivity of ultra-pure anthracite is improved. The electrical conductivity of vacuum heat-treated anthracite is generally much higher than that of untreated anthracite. As the temperature rises, the electrical conductivity increases rapidly from 141.04 S/cm at 300 ℃ to 714.29 S/cm at 1 200 ℃. When the ash content gradually decreases from 3.00% to 0.13%, the electrical conductivities of anthracite at 25 ℃ and 800 ℃ all increase. For coal samples with the same ash content, the electrical conductivity after heat treatment at 800 ℃ is far higher than that at 25 ℃. When the ash content is 3.00%, the electrical conductivity at 25 ℃ and 800 ℃ reaches the minimum values of 2.93 S/cm and 136.99 S/cm respectively; while the ash content is 0.13%, the electrical conductivity at 25 ℃ and 800 ℃ reaches the maximum values of 14.43 S/cm and 1587.30 S/cm respectively. At 800 ℃, the electrical conductivity of anthracite increases with the decrease of ash content is much faster than that of anthracite at 25 ℃, and the gap between the two electrical conductivities increases sharply as the ash content decreases. This demonstrates that increasing the vacuum heat treatment temperature is more effective in improving the electroconductivity of anthracite than reducing its ash content. Vacuum heat treatment causes the volatile matter inside ultra-pure anthracite to be discharged, resulting in a slight increase in its ash content. During the vacuum heat treatment process, the main original minerals in anthracite undergo chemical reactions, namely, mica and kaolinite react with silica to form mullite after removing water and hydroxyl groups, pyrite transforms into magnetite and hematite, ferrous oxide reacts with quartz to produce clinoferrosilite.