Activated coke was prepared by mixing sewage sludge and waste poplar bark biomass from furniture manufacturing. The physical activation method of these feedstocks with steam for 1 h at 850 °C was implemented. The elemental composition, pore distribution, microstructure, and surface functional groups of the activated coke products were analyzed by proximate analysis, ultimate analysis, N2 adsorption, scanning electron microscopy, and Fourier transform infrared spectroscopy, respectively. The effects of different mixing ratios of sludge and biomass, preactivation carbonization temperature, and activation method on the activated coke were investigated. When the proportion of biomass was two-thirds of the total feedstock mass and the carbonization temperature was 300 °C, the produced activated coke had the highest specific surface area and the most extended micropore structure. Water vapor (steam) activation was found to be beneficial to the formation of oxygen-containing functional groups. This study established that steam is beneficial to pore expansion and promotes pore development. It was found that the carbonaceous feedstocks acquired initial porosity through carbonization in nitrogen, which proved to be instrumental in the ensuing activation process. After sequential carbonization and activation, the produced active coke acquired a higher specific surface area and microporosity, compared with the active coke produced by activation alone.