Objective To explore the gut microecology mechanism of modified Jianpi Yangwei Recipe（健脾养胃方） assisting chemotherapy in patients with gastric cancer（GC）. Methods A total of 90 GC patients were divided into observation group（51 cases） and the chemotherapy group（39 cases） according to clinical willing. The control group（63 cases） were recruited from the healthy medical examiners. The chemotherapy group received standard chemotherapy regimen of National Comprehensive Cancer Network（NCCN） Guidelines. The observation group was added with oral administration of modified Jianpi Yangwei Recipe

one dose per day. Both groups were treated for 3 months

and competed 3 sessions of chemotherapy. Life quality score was evaluated before and after treatment. After treatment

fecal microbiomes were tested by high-throughput sequencing based on 16 S rRNA gene. Results After treatment

the life quality score of the observation group was decreased（P < 0. 05）

and there was no significant difference in the chemotherapy group（P > 0. 05）

while the life quality score of patients in the observation group was significantly lower than that of the chemotherapy group（P < 0. 05）. There was no significant difference in intestinal flora diversity between the groups（P > 0. 05）. The intestinal flora of Chao and Ace in the chemotherapy group was significantly lower than that in the control group（P < 0. 05）. The intestinal flora Chao and Ace in the observation group were significantly higher than those in the chemotherapy group（P < 0. 05）. Compared with the chemotherapy group

the relative abundance of symbiotic bacteria in the observation group was significantly lower（P < 0. 05）.Compared with the control group

the relative abundances of the Clostridium order

the Fusarium family

the Prevotella genus

and the Rutococcus genus were significantly decreased in the observation group and the chemotherapy group（P < 0. 05 or P < 0. 01）

while the relative abundances of desulfurization order

symbiotic bacteria order

desulfovibrio family

symbiotic bacteria family

and Conobacteria genus were significantly increased（P < 0. 01）. Compared with the chemotherapy group

the relative abundances of symbiotic bacteria order

symbiotic bacteria family

the Rutococcus genus

the Lachnospiraceae family NK4 A136 group and the Coronaria genus were significantly decreased（P < 0. 05）

while the relative abundance of the Lachnospiraceae family NK4 A136 group was significantly increased（P < 0. 05）. Conclusion Modified Jianpi Yangwei Recipe could reverse the changes of intestinal flora caused by chemotherapy in patients with gastric cancer

thus improving the quality of life of patients.