Objective To evaluate the impact of mesoreetal margin micrometastasis on local recurrence of rectal carcinoma after total mesorectal excision, and the relation between mesorectal margin mierometastasis and local recurrence. Methods Mesorectal margin specimens from 52 cases of rectal cancer after total mesorectal excision were studied by reverse transcriptase-polymerse chain reaction (RT-PCR) to detect the expression of CK20 mRNA. These patients were divided into CK20 mRNA positive and negative group and followed up for 3 years until local recurrence developed. Results In 52 patients with rectal cancer,21 cases were found to express CK20 mRNA in mesorectal margin, the expression rate of CK20 mRNA in Dukes A,B and C was 17% ,30% and 54% (P<0.05), respectively. The positive rate of well differentiated, moderately differentiated, poorly differentiated and undifferentiated carcinomas were 43%, 38% ,40% and 50% ,respectively(P>0.05 ). The incidence of local recurrence in CK20 mRNA positive and negative group was 24% and 3% , respectively. The difference was statistically significant between the two groups (P <0.05 ). Conclusion Detection of mesorectal margin CK20 mRNA as micrometastasis by RT-PCR in rectal carcinoma patients was a sensitive and effective way in predicting local recurrence. It is necessary for patients with positive mesorectal margin CK20 mRNA to undergo postoperative radiotherapy after total mesorectal excision.