To address the corrosion and dendrite issues of lithium metal anodes, a protective layer was ex-situ constructed by P4S10 modification. It was determined by X-ray photoelectron spectroscopy and Raman spectra that the main constituents of the protective layer were P4S10, Li3PS4 and other Li x P y S z type derivatives. The protective layer was proved to be effective to stabilize the interphase of lithium metal. With the modified Li anodes, symmetric cells could deliver stable Li plating/stripping for 16000 h; Li–S batteries exhibited a specific capacity of 520 mA h g−1 after 200 cycles at 1000 mA g−1 with average Coulombic efficiency of 97.9%. Therefore, introducing Li x P y S z based layer to protect Li anode provides a new strategy for the improvement of Li metal batteries.