Objective?To investigate the correlation of routine clinical test indicators, including routine blood test indicators and serum tumor markers, with clinicopathological parameters of colorectal cancer (CRC), and establish a nomogram for the diagnosis and prediction of CRC.?Methods?The clinical data from 370 patients with newly diagnosed CRC were retrospectively analyzed. The correlation of routine clinical test indicators with clinicopathological parameters of CRC patients and their diagnostic efficacy were statistically analyzed. The independent risk factors of CRC were determined by the multivariate Logistic regression analysis. Then, the nomogram model for the diagnosis and prediction of CRC was established and its predictive efficiency was evaluated.?Results?The neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and red blood cell distribution width (RDW) in the patients with CRC were significantly higher than those of healthy controls, while the lymphocyte-to-monocyte ratio (LMR) significantly lower (all?P<0.01). NLR was related to tumor size, T staging, TNM staging, lymph node metastasis and distant metastasis, while PLR was related to sex, tumor location, T staging and lymph node invasion. The AUCROC, sensitivity and specificity of NLR, PLR, RDW and LMR combined with serum tumor markers such as CEA and CA19-9 for the diagnosis of CRC were 0.844, 67.1% and 87.9%, respectively. PLR, RDW, LMR, CEA, CA19-9, age and sex were the independent risk factors of CRC (all?P<0.05), and the C-index of the established nomogram model based on these indicators was 0.866.?Conclusion?The combination of NLR, LMR, PLR, RDW, CEA and CA19-9 is helpful for the early screening of CRC, and the established prediction model has a certain clinical value in the diagnosis of CRC.