Solid-state lithium metal batteries have emerged as promising energy storage systems due to large energy storage density and low-risk safety hazard. However, high-interface resistance between the garnet-based electrolyte and Li metal anode is one of the major challenges for all-solid-state batteries. Herein, a straightforward modification method is reported, rather than relying on hot pressing under an inert atmosphere or high-cost fabrication techniques to produce metastable nano-coating on garnet electrolyte surface. Fresh Li/Co@SSE@Co/Li batteries are placed at room temperature for 48 hours under a tiny pressure of 1 MPa, however the interfacial resistance between the garnet and Li metal reduces from 5,800 – 8,200 Ω cm2 to only 162 Ω cm2. At a current density up to 1.6 mA cm-2, the symmetrical batteries exhibit a stable signal voltage of about 190 mV. The maximum voltage fluctuation is less than 7 mV for the Li/Co@SSE@Co/Li batteries during 160 Li-striping/plating cycles at 0.25 mA cm-2. Excellent electrochemical performance and easy-to-industrial modification method are beneficial for the commercialization of Li metal all-solid-state batteries.