Objective: To analyze the diagnostic value of fecal Fusobacterium nucleatum detection, fecal immunochemical test (FIT), and carbohydrate antigen 19-9 (CA19-9) detection for colorectal cancer (CRC). Method: A total of 78 CRC patients and 60 healthy individuals were enrolled in this study. Stool and blood samples were collected for the 3 diagnoses, and ROC curves were analyzed for diagnostic value. Result: The 3 diagnoses’ positive detection rates in CRC samples were significantly higher than those of healthy samples (P < 0.05). The combined CRC diagnoses showed significantly higher sensitivity as compared to individual fecal F. nucleatum detection (χ2 = 6.495, P = 0.011), FIT (χ2 = 4.871, P = 0.027), and serum CA19-9 detection (χ2 = 7.371, P = 0.007). The area under the ROC curve for fecal F. nucleatum detection was 0.63 [95% confidence interval (CI) = 1.124–6.238], with a sensitivity of 73.08% and specificity of 85.00%, whereas FIT was 0.65 (95% CI = 1.365–9.241), with a sensitivity of 51.28% and specificity of 96.67%, meanwhile, serum CA19-9 detection was 0.62 (95% CI = 1.517–12.342), with a sensitivity of 69.23% and specificity of 98.33%. The combined CRC diagnoses showed an area under the ROC curve of 0.76 (95% CI = 1.213–6.254), with a sensitivity of 87.18% and specificity of 70.00%. Conclusion: The combined diagnoses of fecal F. nucleatum detection, FIT, and serum CA19-9 detection can significantly improve the sensitivity and accuracy of CRC diagnosis, which has high clinical application value to provide guidance for clinical CRC screening and early intervention treatment.