Abstract: Objective To investigate the function of AT motif binding factor 1 (ATBF1) in colorectal cancer. Methods ATBF1 protein expression was detected in 146 pairs of colorectal cancer tissues and the adjacent tissues using immunohistochemistry. ATBF1 protein expression was also examined in colorectal cell lines with laser confocal microscopy. ATBF1-A protein expression in colorectal cancer tissues of different differentiation grades and in the colorectal cancer cell lines were detected with Western blotting. The expressions of ATBF1 mRNA in 38 moderately differentiated colorectal cancer tissues and the paired adjacent tissues and in the colorectal cancer cell lines were tested using RT-PCR. Results ATBF1 protein expression levels in colorectal cancer tissues and adjacent tissues differed significantly (P<0.001), and its expression increased significantly in positive correlation with the grade of tumor differentiation (P<0.001) but in negative correlation with tumor metastasis. ATBF1 mRNA expression and ATBF1 protein expression were significantly correlated (P=0.100). The ATBF1 protein and mRNA expressions also differed significantly among different colorectal cancer cell lines. Conclusion ATBF1 executes the role of a tumor suppressor gene in colorectal cancer, and its protein expression is associated with tumor differentiation and lymph node metastases.