Objective：To analysis the relationship of poorly differentiated clusters（PDC）and tumor buddings（TB）in colorectal adenocarcinoma and MUC1 expression in PDC and TB. To explore the correlation and biologic characteristic of PDC and TB in colorectal carcinoma. Methods：The identification and grading of PDC in 183 cases of colorectal adenocarcinoma were observed by HE staining. The identification and grading of TB were examined by CK immunohistochemical staining. MUC1 expression of PDC and TB was detected by EnVision immunohistochemical method. Results：Among 183 cases of colorectal adenocarcinoma，the detection rate of PDC was 56.8%（104/183），intratumoural budding（ITB） was 54.1%（99/183），and peritumoural budding（PTB） was 62.3%（114/183）. There was a positive correlation between PDC and ITB，PDC and PTB in colorectal adenocarcinoma（P < 0.001）. PDC grade was positively correlated with PTB grade（P < 0.05），but not with ITB grade（P > 0.05）. MUC1 was mainly expressed in the lumen margin and/or cytoplasm in the main body of the tumors，while in PDC and TB，MUC1 was expressed in the reverse mode，i.e. I/O mode. The reverse expression rates of MUC1 in PDC，ITB and PTB were 55.8%，58.6% and 54.4%，respectively. Conclusion：PDC and TB，especially PTB，were closely related in colorectal adenocarcinoma which suggested that their biological behaviors were closely related. Reverse expression patterns of MUC1 in PDC and TB suggested that they may have the characteristics of micropapillary carcinoma，which may be different stages of micropapillary carcinogenesis.