Objective:To evaluate the clinical efficacy of Guizhi Mahuang Geban Decoction combined with conventional western medicine in the treatment of post infections cough (PIC), and to explore the mechanism.Methods:A total of 100 PIC patients in our hospital from January 2020 to July 2021 who met the inclusion criteria were divided into 2 groups according to the random number table method, with 50 in each group. The control group was treated with conventional western medicine, and the study group was treated with Guizhi Mahuang Geban Decoction and the treatment of the control group. Both groups were treated for 10 days. TCM symptom scores were performed before and after treatment. The levels of neurokinin A (NKA), substance P (SP), neurokinin B (NKB) and calcitonin gene related peptide (CGRP) were detected by ELISA. Adverse events were recorded and clinical effects were evaluated.Results:The total clinical effective rate was 90.0% (45/50) in the study group and 68.0% (34/50) in the control group, and there was significant difference between the two groups ( χ2=7.29, P=0.007). The scores of cough, expectoration, pharyngeal itch and total score in the study group were significantly lower than those in the control group ( t values were 8.04, 6.30, 9.03, 9.71, all Ps<0.01). After treatment, NKA [(86.08±18.21) ng/L vs. (137.68±28.29) ng/L, t=10.85], SP [(54.23±11.28) ng/L vs. (71.75±15.34) ng/L, t=6.51], NKB [(96.15±20.19) ng/L vs. (149.84±30.22) ng/L, t=10.45], CGRP [(62.93±18.35) ng/L vs. (89.59±23.25) ng/L, t=6.37] levels in the study group were significantly lower than those in the control group ( P<0.01). The incidence of adverse events was 8.0% (4/50) in the control group and 10.0% (5/50) in the study group, and there was no significant difference between the two groups ( χ2=0.13, P=0.727). Conclusions:Compared with western medicine alone, Guizhi Mahuang Geban Decoction combined with western medicine can rapidly improve patients' symptoms, improve curative effect and have better safety for PIC. Its mechanism may be related to the regulation of NKA, SP, NKB and CGRP levels.