〔Abstract〕 Objective To study the expression and clinical significance of CD155 protein in pancreatic ductal adenocarcinoma tissues and adjacent normal tissues, as well as in pancreatic cancer cell lines. Methods Immunohistochemistry was used to detect the expression of CD155 in paraffin-embedded tissues and non-carcinoma adjacent tissues from 92 cases of pathologically confirmed pancreatic ductal adenocarcinoma.And the relationship between CD155 and clinical pathological parameters was analyzed. Western blot and qRT-PCR methods were also used to detect the expression of CD155 in normal pancreatic cells(HPDE6-C7) and three pancreatic cancer cells(Panc-1, BxPC-3, AsPC-1). Results The results of immunohistochemistry showed that CD155 was mainly expressed on the cell membrane of pancreatic ductal adenocarcinoma tissues. The positive expression rate of CD155 in pancreatic ductal adenocarcinoma tissues was 65.22%(60/92), while the positive expression rate in normal tissues adjacent to the cancer was 38.04%(35/92), the difference in positive expression between the two groups was statistically significant(χ2=13.60,P<0.01);The expression of CD155 was ralated to the degree of pancreatic ductal adenocarcinoma differentiation(P<0.001), neural infiltration(P<0.001), and lymph node metastasis(P=0.001); Westen blot and qRT-PCR results showed that the expression levels of CD155 protein and mRNA in three pancreatic cancer cells were higher than those in normal pancreatic cells, and the differences were statistically significant compared with normal pancreatic cells(P<0.01). Conclusion The expression of CD155 is correlated with the degree of pancreatic ductal adenocarcinoma differentiation, nerve invasion and lymph node metastasis. The detection of CD155 is used to evaluate the severity of pancreatic ductal adenocarcinoma patients. At the same time, CD155 is highly expressed in pancreatic cancer cells. It may be possible to use CD155 to bind to the immune cell activating receptor DNAM-1 to initiate the activation and killing effect of immune cells on pancreatic cancer and provide new ideas for immunotherapy of pancreatic cancer.