Woody biomass, as an important renewable resource, can serve as a substitute for petroleum-based feedstocks. Lignocellulose is the main component of woody biomass, primarily consisting of cellulose, hemicellulose, and lignin. The hierarchical structure of lignocellulose and the interactions between its components render efficient separation particularly challenging. The separation and conversion of components into advanced materials is an essential pathway for achieving their high-value transformation. This review first highlights the structural and chemical characteristics of each component that are most relevant to functional material design and then summarizes recent progress in advanced separation strategies, including cellulose-targeted separation strategy, the hemicellulose-first, and the lignin-first. These strategies are further linked to the development of electromagnetic interference (EMI) shielding materials, demonstrating that the properties of different components influence filler dispersion, conductive network formation, and porosity. Cellulose is assembled into a hydrogen-bonded scaffold to promote the uniform distribution of the filler. Lignin is utilized for its aromatic skeleton to enhance dielectric loss and interfacial coupling. By combining conductive pathways with interfacial polarization and multiscale scattering, effective EMI shielding can be achieved in thin films, paper, and aerogels. This separation-to-function framework provides practical guidance for designing sustainable, high-performance EMI shielding materials derived from lignocellulosic biomass.