Abstract： Objective： To observe the clinical effect of modified Sijunzi Decoction combined with FOLFOX4 chemotherapy regimen on patients with advanced colorectal cancer with predominant dampness due to spleen deficiency syndrome. Methods： A total of 60 cases of patients with advanced colorectal cancer with predominant dampness due to spleen deficiency syndrome were selected as research objects and divided into the control group and the observation group according to the random number table method， with 30 cases in each group. Both groups were treated with FOLFOX4 chemotherapy regimen， and the observation group was additionally treated with modified Sijunzi Decoction. Both groups were treated for three months. Before treatment and after 3-month treatment， traditional Chinese medicine (TCM) syndrome scores were assessed； tumor markers [carcinoembryonic antigen (CEA)， carbohydrate antigen (CA199)] were detected； health status [karnofsky performance status (KPS) score] was evaluated. The clinical effects were compared between the two groups. During treatment， the incidences of adverse reactions in the two groups were recorded. Results：After three months of treatment，the total effective rate was 83.33% in the observation group，higher than that of 56.67% in the control group，the difference being significant (P＜0.05). The scores of abdominal distension after meal，torpid intake，fatigue，lack of strength and loose stool and the total scores of TCM syndrome in the two groups were decreased when compared with those before treatment (P＜0.05). The scores of abdominal distension after meal， torpid intake，fatigue，lack of strength and loose stool and the total scores of TCM syndrome in the observation group were lower than those in the control group (P＜0.05). The values of CEA and CA199 in the two groups were decreased when compared with those before treatment (P＜0.05)，and the values of CEA and CA199 in the observation group were lower than those in the control group (P＜0.05). KPS scores in the two groups were increased when compared with those before treatment (P＜0.05)， and the KPS score in the observation group was higher than that in the control group (P＜0.05). The incidence of adverse reactions was 40.00% in the observation group，lower than that of 73.33% in the control group，the difference being significant (P＜0.05). Conclusion： Modified Sijunzi Decoction combined with FOLFOX4 chemotherapy regimen has a significant clinical effect in the treatment of patients with advanced colorectal cancer with predominant dampness due to spleen deficiency syndrome，which can not only effectively alleviate clinical symptoms and inhibit the progression of disease，but also improve the health level of patients and enhance the treatment safety.