Objective To evaluate the efficacy and safety of Huoxiang Zhengqi Oral Liquid（藿香正气口服液） in treatment of gastrointestinal flu of summer-dampness syndrome. Methods A prospective randomized

double blinded

placebo-controlled and multicentered clinical trial was conducted in 20 clinical centers in China. The 240 subjects confirmed of summer-dampness syndrome of stomach and intestine type enrolled were randomly divided into 3 groups

with 80 cases in each group. A high dose group treated with Huoxiang Zhengqi Oral Liquid 20 ml

twice a day; a low dose group treated with Huoxiang Zhengqi Oral Liquid 10 ml and Huoxiang Zhengqi Oral Liquid mimetic agent 10 ml

twice a day; and a placebo group treated with Huoxiang Zhengqi Oral Liquid mimetic agent 20 ml

twice a day. All the groups were treated for 5 days. The main efficacy indexes including recovery rate on the third day and the time of disease recovery

the secondary efficacy indexes including total score of gastrointestinal flu symptoms

total score of traditional Chinese medicine（TCM） symptoms and syndrome effectiveness

the disappearance rate of single symptoms of TCM and adverse reactions were observed. Results In the high dose group

low dose group and placebo group

the 3-day cure rates was 72.00%

37.33% and 14.29% respectively. The differences are statistically significant（P<0.05）. Compared with the superiority test

the 95% CI lower limit of the difference in recovery rate between the groups was greater than 0

and the superiority was established. The median illness cure-time were 2.0

4.0 and 5.0 days respectively

and the total scores of symptoms after 3-day treatment were 1.04±1.70

2.70±2.50 and 3.69±2.65 respectively; the total scores of TCM symptoms after 5-day treatment were 0.45±0.96

0.69±1.46 and 1.39±2.15 respectively

and the effective rates of TCM symptoms after 5-day treatment were 100.00%

100.00% and 90.91% respectively. The differences of the groups mentioned above were statistically significant（P<0.05）. Meanwhile

there were significantly statistical differences in the 3 groups in the disappearance rate of single symptom such as nausea and/or vomiting

body trapped（P<0.05）. No related adverse effects were reported in 3 groups during the treatment. Conclusion Huoxiang Zhengqi Oral Liquid can improve the clinical symptom of gastrointestinal type flu of summer-dampness syndrome

shorten the course of disease with high safety.