To assess the inflammatory response and side effects of chemotherapy combined with Shenmai injection (SMI) in the treatment of patients with advanced colorectal cancer (CRC). This retrospective cohort study included the clinical data of 152 patients with advanced CRC admitted to the First Affiliated Hospital of Huzhou University from April 2020 to April 2023. The patients were divided into control group (patients received chemotherapy treatment, n=75) and observation group (patients received chemotherapy combined with SMI, n=77) based on the treatment received. Tumor control rate, levels of immune function indicators before and after treatment, levels of inflammatory factor indicators, and incidence of toxic side effects in two groups were analyzed. Tumor control rate in the observation group (89.61%) was higher than that in the control group (77.33%) (P<0.05). After the treatment, the levels of CD3+, CD4+, CD4+/CD8+in both groups were significantly higher than before the treatment, and significantly higher in the observation group compared to the control group (P<0.05). After the treatment, serum levels of interleukin 6 (IL-6), tumor necrosis factor-alpha (TNF-α), and interleukin-8 (IL-8) in both groups decreased compared to pretreatment levels, and was significantly lower in the observation group (P<0.05). The incidence of adverse reactions in the observation group was significantly lower than that in the control group (P<0.05). Compared with chemotherapy alone, chemotherapy combined with SMI better alleviates inflammatory response in patients with advanced CRC, enhance immune function, and improve tumor control rate, with a lower incidence of toxic side effects.