The article presents the research results of electromagnetic radiation reflection and transmission characteristics in the frequency range 0.7–17.0 GHz of the hydrolytic lignin, impregnated to saturation with the electrolyte water solution, at different temperatures of this material. The research is aimed at simultaneously solving of two problems: 1) search for new inexpensive materials for electromagnetic shielding; 2) experimental substantiation of a new promising method of hydrolysis lignin utilization. Based on the research results, it is possible to conclude the hydrolytic lignin is prospective for use for the manufacture of moisture-containing materials that attenuate electromagnetic radiation energy. Such materials could be used in the architectural electromagnetic shielding systems (including in the systems operating under conditions other than standard) in the form of filler for air gaps of walls and floors or filler for the building mixtures. In practice, such systems are used for protection radioelectronic equipment or people, located inside of the buildings, from the impact of external electromagnetic radiation.