In recent years, more and more people have realized the importance of green and sustainable development. Wood as the most abundant natural biodegradable material on the earth, the preparation of high strength transparent wood (TW) by filling the delignified wood (DW) with resin is a hot research topic at present. Taking this as inspiration, here gel polymer electrolytes (GPEs) with high ionic conductivity were prepared by using DW as substrate, polyurethane (PU) with different ratios of polyethylene glycol (PEG) to 2,2-bis(hydroxymethyl)propionic acid (DMPA) as filling polymer matrix and lithium perchlorate (LiClO₄) as electrolyte through vacuum perfusion method, and applied in solid-state supercapacitors (SCs) with activated carbon as working electrodes. The cell cavity retained in DW provided a controllable ion transport channel, which further improved the efficiency of ion transport and storage. The synthesized DW-PU_1.00-GPE possessed a splendid ionic conductivity of 2.90 × 10⁻² S cm⁻¹ at room temperature (RT). The solid-state SCs assembled with the DW-PU_1.00-GPE also displayed the highest specific capacitance of 157.7 F g⁻¹ at 0.3 A g⁻¹, the outstanding E_cell of 11.49 W h kg⁻¹ and a long cycling life of 4000 cycles with 95 % capacitance retention and nearly 100 % coulomb efficiency. The DW-PU-GPEs achieve efficient Li⁺ transport with the help of rich internal cavities, especially showing excellent ion conductivity which possess a great development prospect in the application of SCs and broaden the application of wood in the field of electrochemistry.