Vacuum carbon dust (VDC) can be used to replace part of calcined coke in the route of prebaked carbon anode, which can realize high-value resource utilization of carbon residue. However, its influence on the reactivity of anode raw materials and its action mechanism are still unclear, which is the technical bottleneck of realizing its utilization. In this paper, the carbon dust was vacuum distilled at 1200℃ and the vacuum degree was 0.5~5Pa. Then it would be added to the anode and the reactivity was tested. The results show that the increase of VDC reduces the anode reactivity of in air atmosphere (600℃),which show catalysis in CO2 atmosphere (970℃). By studying the influence of VDC on the pyrolysis process of coal tar pitch and the reactivity, structure and catalysis of anode raw materials, it was found that the change of anode reactivity was caused by the joint action of chemical factors and structural factors. Firstly, VDC increases the coking rate of asphalt, the crystallite height of coke, and increases the graphitization degree, which reduce the reduction of reactivity of raw materials. Secondly, the Ca in VDC plays a catalytic role in the gasification reaction of carbon raw materials, and this catalytic role becomes more obvious with the increase of temperature. When the temperature is 970℃, the Ca in VDC has a very strong catalytic effect on modified pitch coke, which is the main reason for the increase of anode CO2 reactivity.