Heat stress (HS) may induce immunosuppression as well as inhibit the proliferation of lymphocytes. This study evaluated the effects on immune function of our prescription on splenic lymphocytes under HS as well as its compatibility. The effects of four herbal extracts from Agastache rugosa, Atractylodes lancea, Cortex Phellodendri, and Gypsum Fibrosum on heat treated splenic lymphocytes were investigated and the compatibility of the prescription was also explored by using the Taguchi method. This study revealed changes in proliferation by traditional Chinese medicines of splenic lymphocytes after HS. Proliferation in the HS group was significantly lower than the control group. Under HS, the effects of higher concentrations of Agastache rugosa (100 and $200{mu}g/mL$), Atractylodes lancea (100 and $200{mu}g/mL$), Cortex Phellodendri (50 and $100{mu}g/mL$) and Gypsum Fibrosum (100 and $200{mu}g/mL$) caused a significant increase on ConA/LPS-induced proliferation of lymphocytes than lower concentrations. We, therefore, conclude that the prescription of traditional Chinese medicines may recover splenic lymphocytes from the immunosuppression induced by HS. The Taguchi design, which allows rapid and high efficiency for the selection of the best conditions for our prescription on HS-treated splenic lymphocytes, demonstrated that Agastache rugosa ($200{mu}g/mL$), Atractylodes lancea ($200{mu}g/mL$), Cortex Phellodendri ($100{mu}g/mL$) and Gypsum Fibrosum ($100{mu}g/mL$) were the optimal conditions for the prescription. The validation experiment confirmed that our composition in optimum extraction conditions enhanced effects on ConA or LPS-stimulated lymphocytes under HS. The results showed that the Taguchi optimization approach is a suitable method for optimization of the composition of prescription.