Objective To evaluate the therapeutic effect and research the possible mechanism of Yiqi Jiedu Granules（ qi-boosting toxin-resolving granules） combined with western medicine for herpes simplex keratitis（ HSK）. Methods Totally 213 cases（ 217 eyes） of HSK were randomized into the control group of 106 cases（ 108 eyes） and treatment group of107 cases（ 109 eyes）. The control group was given 0. 15% ganciclovir eye drops and symptomatic treatment. The treatment group was added with 20 g Yiqi Jiedu Granules twice daily. The therapeutic effect was evaluated after 4-week treatment. The symptoms

signs

corneal sensitivity

corneal lesion and recurrence within 1 year were observed in both groups. The levels of CD4 and CD8 were detected. Results The cure rate

significant efficiency and effectiveness were 53. 21%

26. 61% and 20. 18% in the treatment group and 28. 70%

38. 89% and 32. 41% in the control group

with significant difference between groups（ P = 0. 001）. The eyes of sensitivity

retardation and disappearance of corneal sensation in both groups were significantly decreased after treatment（ P < 0. 05）

especially in the treatment group（ P < 0. 05）. The healing index of corneal lesion in the treatment group was superior to that in the control group after treatment（ P < 0. 01）. There were significant differences between groups in the levels of CD4

CD8 and CD4 / CD8 after treatment（ P < 0. 01）. The 1-year cumulative recurrence rate in the treatment group and control group was 20. 5% and 38. 00% respectively

with a significant difference between groups（ P < 0. 01）. Conclusion The combo therapy of Yiqi Jiedu Granules and western medicine can obviously relieve the symptoms and signs

reduce recurrence

increase CD4 expression and decrease CD8 expression as compared with single western medicine therapy and the regulation of immune function may be one of its mechanisms.