Solid electrolyte is vital to ensure all-solid-state batteries with improved safety, long cyclability, and feasibility at different temperatures. Herein, we report a new family of amorphous solid electrolytes, xLi2O-MCly(M = Ta or Hf, 0.8 ≤ x ≤ 2, y = 5 or 4). xLi2O-MClyamorphous solid electrolytes can achieve desirable ionic conductivities up to 6.6 × 10−3S cm−1at 25 °C, which is one of the highest values among all the reported amorphous solid electrolytes and comparable to those of the popular crystalline ones. The mixed-anion structural models of xLi2O-MClyamorphous SEs are well established and correlated to the ionic conductivities. It is found that the oxygen-jointed anion networks with abundant terminal chlorines in xLi2O-MClyamorphous solid electrolytes play an important role for the fast Li-ion conduction. More importantly, all-solid-state batteries using the amorphous solid electrolytes show excellent electrochemical performance at both 25 °C and −10 °C. Long cycle life (more than 2400 times of charging and discharging) can be achieved for all-solid-state batteries using the xLi2O-TaCl5amorphous solid electrolyte at 400 mA g−1, demonstrating vast application prospects of the oxychloride amorphous solid electrolytes.