BACKGROUND: Colorectal cancer, which originates from the human colon or rectum, is one of the leading causes of death worldwide. Timely diagnosis and interventional therapy can significantly improve the prognostic survival of colorectal cancer patients, making regular screening and early detection essential. AIM: To investigate the regulatory function of lncRNA CTBP1-DT (CTBP1-DT) on colorectal cancer cells and to assess its diagnostic significance. METHODS: A total of 102 patients with colorectal cancer and 92 healthy individuals were selected. The levels of CTBP1-DT and microRNA-30a-5p (miR-30a-5p) in serum and cell samples of the above subjects were compared by RT-qPCR. The effects of CTBP1-DT and miR-30a-5p dysregulation on the biological functions of colorectal cancer cells were analyzed via CCK-8, flow cytometry and Transwell assays. In addition, the ability of CTBP1-DT and miR-30a-5p to early identify colorectal cancer patients was determined through ROC curve. RESULTS: Serum CTBP1-DT was elevated in patients with colorectal cancer, which was obviously higher than in healthy controls. The expression of serum miR-30a-5p was downregulated in colorectal cancer. Both CTBP1-DT and miR-30a-5p have the value of distinguishing colorectal cancer, and the combined diagnostic ability is higher. Knockdown of CTBP1-DT directly targeted miR-30a-5p to repress cell activity and metastatic ability, whereas deregulation of miR-30a-5p eliminated the above inhibitory effects. CONCLUSION: Overexpression of CTBP1-DT has a certain application potential in the diagnosis of colorectal cancer and may be a therapeutic target for colorectal cancer.