Abstract: Objective To investigate the expression of anchor attachment protein (AAP) in colorectal carcinoma tissues and serum levels of AAP in colorectal carcinoma patients and to study the relationship between AAP expression and lymph node and liver metastases. Methods Immunohistochemistry was used to detect AAP expression, and enzyme linked immunosorbent assay was used to test AAP levels in peripheral vein blood in 83 patients with colorectal carcinoma. Results The expression rates in normal colorectal mucosa, primary cancer, lymph nodes and liver metastases were 20.5%、53.0%、69.8% and 80.0%, respectively. The positive rates of AAP in primary cancer, lymph nodes and liver metastases were higher than that in normal mucosa (P＜0.01). The positive rates of AAP in lymph nodes and liver metastases were higher than that in primary cancer (P＜0.05). The AAP expression in primary cancer with lymph node and liver metastases were higher than that without metastases (P＜0.01). The mean serum level of AAP in 83 patients was (6.3±2.8)μg/L, which was obviously higher than that in control of 30 healthy volunteers (P＜0.01). The serum level of AAP in patients with Dukes C and D was (7.1±2.9)μg/L, which was markedly higher than that with Dukes A and B (5.2±2.6)μg/L (P＜0.05). Conclusions Monitoring the serum level in patients with colorectal carcinoma is important in prediction and diagnosis of pathogenetic condition and liver metastasis.