All-solid-state lithium batteries (ASSLBs) are promising for safety and high-energy-density large-scale energy storage. In this contribution, we propose a Li_3–4xZr_xPS₄ (LZPS) by Zr-doped β-Li₃PS₄ (LPS) as a novel solid electrolyte (SE) for ASSLBs based on experimental and simulation methods. The structure, electronic property, mechanical property, and ionic transport properties of LZPS (x = 0, 0.03, 0.06, and 0.1) are investigated with first-principles calculations. Meanwhile, LZPS is prepared by solid states reaction method. By combining experimental analysis and first-principles calculations, it is confirmed that a small amount of Zr⁴⁺ can be successfully doped into the framework of β-LPS composites without significantly compromising structural integrity. When the Zr⁴⁺ concentration is x = 0.03, the doped material Li_2.88Zr_0.03PS₄ exhibits the highest ionic conductivity (5.1 × 10⁻⁴ S·cm⁻¹) at 30 °C, and the Li-ion migration energy barrier is the lowest. The Li_2.88Zr_0.03PS₄ SE has obtained the best mechanical properties, the good ductility, and shear deformation resistance, which can better maintain the structural stability of the battery. In addition, the Li/Li symmetrical cell is assembled, which shows excellent electrochemical stability of electrolyte against lithium. The constructed all-solid-state batteries (LiCoO₂-Li₆PS₅Cl|Li_2.88Zr_0.03PS₄|Li-In) delivers an initial discharge capacity of 130.4 mAh·g⁻¹ at 0.2 C and a capacity retention of 85.1% after 100 cycles at room temperature. This study provides a promising electrolyte for the application of ASSLBs with high ionic conductivity and excellent stability against lithium.