Abstract: Objective To investigate the clinical significance of differential human mcl1 subtypes expression in colorectal cancer tissues. Methods The differential expression of three mRNA splicing variants and protein subtypes of mcl1 were detected in each 20 cases of normal colon tissues, colorectal adenoma, colorectal adenocarcinoma and their relative para-carcinoma tissues using RT-PCR and Western blot, and then we further analyzed the relationship of these variants expression with clinicopathological characteristics in the colon tumors. Results The expression of subtypes 1 and 2 of mcl1 were higher in colon tumor tissues and relative para-carcinoma tissues than those in normal control, and higher in the adenocarcinoma tissues than those in adenoma tissues . The expression of subtype 3 of mcl1 were higher in colon tumor tissues and relative para-carcinoma tissues than those in normal control, but no statistical significance in the comparison between tumor tissues and their relative para-carcinoma tissues as well as the comparison between adenocarcinoma tissues and adenoma tissues. Conclusion The subtypes 1 and 2 of mcl1 expression are demonstrated as a positive correlation with the malignancy level of colon tumor and could be used as efficient biomarkers in clinical diagnosis. The subtypes 3 could be used as an early biomarker for colon tumor diagnosis, while its expression has no significant correlation with the malignancy level of colon tumor.