Objective To investigate the effect of postoperative parenteral and parenteral nutritional support on immunity and intestinal flora in patients with colorectal cancer. Method A total of 90 patients with colorectal cancer who were treated in the First Affiliated Hospital of Hebei Northern University from January 2019 to May 2021 were selected. All patients were divided into a control group and a research group by random number table method with 45 cases in each group. The control group was given parenteral nutrition intervention and the research group was given enteral nutrition combined with parenteral nutrition intervention. The nutritional status CD cells immune proteins intestinal flora levels and clinical indicators before and after intervention were compared between the two groups. Result There was no significant difference in the levels of serum total protein TP serum albumin ALB transferrin Tf hemoglobin Hb and body mass index BMI between the two groups before the intervention P>0. 05 after the intervention the levels of TP ALB Tf Hb and BMI in the research group were significantly higher than those in the control group P<0. 05 . The levels of CD3 + CD4 + and CD4 + / CD8 + in the two groups before intervention were not significantly different P>0. 05 the levels of CD3 + CD4 + and CD4 + / CD8 + in the research group after the intervention were significantly higher than those in the control group P< 0. 05 . There was no significant difference in the levels of IgA IgG and IgM between the two groups before the intervention P> 0. 05 after the intervention the levels of IgA IgG and IgM in the research group were significantly higher than those in the control group P<0. 05 . There was no significant difference in the number of Lactobacillus Bacteroides Eubacterium Bifidobacterium Coccobacillus and Escherichia coli between the two groups before the intervention P>0. 05 after the intervention the number of Lactobacillus Bacteroides and Bifidobacterium in the research group was significantly higher than that in the control group and the number of Coccobacillus and Escherichia coli was significantly lower than that in the control group P<0. 05 . The eating time anal exhaust time and hospitalization time of the research group were significantly lower than those of the control group P<0. 05 . Conclusion Enteral nutrition combined with parenteral nutrition support can effectively improve the cellular and humoral immune function of the colorectal cancer patients regulate the intestinal flora improve the clinical indicators and promote the postoperative recovery of the patients.