Using HE, AB/PAS, HID/AB, PAT/KOH/PAS stain and CEA monoclonal antibody BA stain techniques, composition of mucin and distribution of CEA in the tumor tissue were detected in 65 cases of colorectal tubular adenoma, 7 adenoma with malignant change and 14 established tubular adenocarcinoma in order to study the functional changes of colorectal adenoma and its relation with the colorectal adenocarcinoma. According to Konishi's criteria, colorectal tubular adenomas were divided into three groups: mild, moderate and severe dysplasia, added with two of ours: adenoma with malignant change and established adenocarcinoma, totalling 5 groups for comparison. The results showed that CEA positive rate increased with the grade of dysplasia in these 5 groups (33%, 57%, 67%, 86% and 100%). Similarly, the percentage of non-acetylated acid and C7 C9 O-acetylated sialomucin also gradually increased with the grade of dysplasia, showing a parallel tendency. Epithelial cells, secreting a heterogeneous mucin, could be taken as a signal of abnormal cellular differentiation. The increase of non-acetylated acid and C7 C9 O-acetylated sialomucin in colorectal adenoma implies a likelihood of malignant change.