Based on the experimental results, three basic conclusions are summarized for the thermal/electric-field poling (TEFP) silica materials, with which the second-order nonlinear optical coefficient in the bulk silica glass after TEFP is calculated, and relationships between the coefficient and the applied voltage V ₀ in the poling process and the thickness of the nonlinear layer created from the poling are obtained. Theoretical results show that the second-order susceptibility χ⁽²⁾ and the second-harmonic efficiency η in the poled bulk glass are proportional to √V ₀ and V ₀², respectively; χ⁽²⁾∼0.2−1.6 pm/V for the bulk glass after the typical TEFP; χ⁽²⁾ decreases with an increase in the poling time after the TEFP silica glass approximately reaches the steady state. Theoretical results are well consistent with the experimental reports.