The invention relates to an active carbon fiber composite material and a preparation method of the active carbon fiber composite material. The active carbon fiber composite material is formed by compounding an active carbon fiber layer and a silica gel layer covered outside the active carbon fiber layer, is large in specific surface area, light in gram weight and high in mechanical strength, not only maintains the high absorption property and flame-retardant property of the active carbon fiber, but also has the large specific surface area and very low heat conduction performance of silica aerogel, and has the characteristics of heat insulation, toxin prevention and flame-retardant property. The preparation method of the active carbon fiber composite material comprises the steps of: dipping the active carbon fiber layer into silica sol, then taking out the active carbon fiber layer, and drying to obtain the active carbon fiber composite material. The preparation method has the advantages of being simple and feasible as well as low in cost.