Abstract <p>The laser-induced damage threshold (LIDT) of optical components is a key parameter for evaluating their resistance to laser damage. Fused quartz is one of the most widely used optical materials. This study investigates the LIDT of quartz substrates with different thicknesses through both theoretical simulations and experimental measurements, aiming to reveal the underlying damage mechanisms. Numerical simulations were conducted to analyze the temperature field distribution of quartz substrates with thicknesses ranging from 1 to 4 mm under 1064 nm nanosecond laser irradiation. Generally, under identical conditions, a higher temperature rise corresponds to a lower LIDT. The simulation results show that as the substrate thickness increases, the LIDT decreases first, then increases, and finally decreases again. Laser-induced damage threshold experiments were subsequently performed, showing that the 1 mm thick quartz substrate exhibited the highest LIDT (30.02 J/cm²), which dropped to its minimum value (4.54 J/cm²) at 2.5 mm and then increased to 17.97 J/cm² with further thickness growth. The experimental results show a certain degree of consistency with the numerical simulations in terms of the overall variation trend, although discrepancies remain in specific thickness ranges. These findings provide theoretical and practical insights into the thickness optimization and damage-resistance design of optical components.</p>