The present study was to investigate the chemopreventive effect of green tea on the precancerous lesion of colorectal cancer in rats based on a series of biomarkers.Twenty four Wistar rats were randomly divided into 3 groups,8 rats for each.Rats in the positive control group were subcutaneously injected with a carcinogen(DMH)from the second week,once a week for 10 weeks.Animals in tea-drinking group were given the same treatment as the positive control group and received 2% green tea as drinking water during the whole study.Rats in the negative control group were subcutaneously injected with the same volume of saline.Rats in the positive control group and the negative control group received tap water as drinking water during the whole study.The results showed that tea-drinking significantly reduced the number of aberrant crypt foci(ACF),the putative precancerous lesions of colorectal cancer(P<0.05).The number of silver-stained nucleolar organizer dots per nucleus(AgNORs)and labeling index(LI)of proliferating cell nuclear antigen(PCNA)of intestinal mucosa in the tea-drinking group were also significantly reduced as compared with those in the positive control group(P<0.05).In addition,tea-drinking inhibited the expression of Bcl-2 protein and induced the expression of Bax protein.In conclusion,green tea had a chemoprophylactic effect on the precancerous lesions of colorectal cancer.The possible mechanisms may be the inhibition of cell preliferation and induction of apoptosis.