Ta-doped lithium-lanthanum-zirconium-oxygen (Li_6.5La₃Zr_1.5Ta_0.5O₁₂, LLZTO) solid electrolytes with a high ionic conductivity at room temperature were prepared by the solid-phase reaction method, and the effects of irradiated electron beams on their structure and properties were investigated in detail. The results showed that no other heterogeneous phases were produced after irradiation with different doses (250 kGy and 500 kGy) of electron beams, and the lattice spacing became larger with an increase in the dose, which is conducive to the reduction of the diffusion energy barrier of ions in the lattice. First-principles calculations revealed that the Li⁺ diffusion energy barrier of the low-dose electron-beam irradiated sample was reduced by 0.07 eV compared with that of the unirradiated sample, suggesting that the defects created by irradiation can promote Li⁺ diffusion. An AC impedance test of the electrolytes before and after irradiation further confirmed that low-dose electron beam irradiation is beneficial for enhancing their ionic conductivity. Exploring the effect of electron beam irradiation on the structure and conductivity of LLZTO oxide solid state electrolytes holds significance in the study of solid state electrolytes.