Objective To screen the optimal parameters for depilation in SD rats, and to provide an experimental prerequisite for the establishment of animal models of skin photoaging. Methods The effects of concentrations and time of the chemical depilatory Na₂S treatment on the hair removal efficiency were evaluated by the number of residual hair per milimeter square and the damaged area of the skin in rats, and the parameters for hair removal were further optimized by D-optimal design. Results Working concentration of Na₂S was the critical factor affecting its capability of hair removal. No depilation was observed when the concentration of Na₂S was lower than 5%, while skin damage began to appear and became severe gradually when the concentration of Na₂S was above 7%.Therefore, 6% Na₂S was taken as the basic concentration for depilation. Hair removal was observed with 6% Na₂S treatment for 5 min. After 10 min of treatment, the surface of the skin turned to be smooth, and this tendency continued until 15 min. After 15 min, skin damage occurred and turned more severe after 20 min. When treated for over 25 min, skin damage similar to skin burns was observed with naked eyes. Overall, our study with the D-optimal design showed that the effect of hair removal in the SD rats was optimal when treated with 7% Na₂S for 10 min, causing no skin damage and residual hair left. Conclusions Highly efficient hair removal in SD rats can be achieved with chemical depilatory optimized by D-optimal design.