〔Abstract〕 Objective To explore the effects of interleukin(IL)-17/interleukin-17 receptor(IL-17R) on the angiogenesis of the endothelial cells co-cultured with cancer cells through DLL4-Notch signaling pathway and its molecular mechanism.Methods Cancer-endothelial cell co-culture model was established using the Transwell system. The effects of human recombinant IL-17A at 50 ng/ml on the migration of human umbilical vein endothelial cells(HUVECs) in the co-culture system were determined, the proliferation and angiogenesis of HUVECs was observed in co-culture system stimulated by human recombinant IL-17A, the angiogenesis ability of HUVECs was tested by tube formation assay, the proliferation of HUVECs was detected using CCK-8 assay. The expression of DLL4-Notch signaling pathway and angiogenesis protein in each group were detected by Western blot.Results 50 ng/ml human recombinant IL-17A could promote the migration of HUVECs in co-culture system. Treatment with 50 ng/ml human recombinant IL-17A significantly enhanced the proliferation and angiogenesis ability of the HUVECs in coculture system(P<0.01). The expression of DLL4-Notch signaling pathway and angiogenesis-related proteins in co-culture system significantly increased compared with those in control group.Conclusion IL-17/IL-17R promotes DLL4-Notch signaling pathway in the angiogenesis of papillary thyroid carcinoma.