Objective:To study the classification of colorectal cancer tissue microvascular and the relationship between intratumoral microvascular density (MVD) and bevacizumab plus chemotherapy sensitivity in advanced colorectal cancer. Methods:Retrospective analysis was used to analyze 33 cases of advanced colorectal cancer treated with bevacizumab plus chemotherapy. Paraffin－embedded tumor samples were sectioned and stained immunohistochemically for the blood vessel markers CD34 and CD31 to characterize the intratumoral vasculature,then MVD were detected. Results:More blood vessels were stained by anti－CD31 antibody than anti－CD34 antibody. Two distinct types of microvascular were identified in colorectal cancer:differentiated (CD31+/CD34+) and undifferentiated (CD31+/CD34-). In the sensitive group,the number of undifferentiated－vessel MVD was 10.6 ± 3.1,significantly higher than 6.9 ± 3.7 in the insensitive group(P < 0.05). The median of each type of vessel was used as the cutoff value to divide the patients into high－ and low－MVD groups. Increased progression－free survival was seen in patients with high undifferentiated－vessel MVD(9.5 months vs. 3.0 months,P < 0.05). Conclusion:CD31+/CD34- MVD can be used as an important biology index to indicate the sensitivity to bevacizumab plus chemotherapy in metastatic colorectal cancer.