Objective:To investigate the influences of circular RNA(circRNA)BICD2 on the proliferation,apoptosis and epitheli-al-mesenchymal transition(EMT)of oral squamous cell carcinoma(OSCC)cells by regulating the miR-218-5p/Ras homolog gene family member A(RhoA)axis.Methods:qRT-PCR and Western blot were applied to detect CircBICD2,miR-218-5p gene expres-sion and RhoA protein expression in OSCC tissue,paracancerous tissue,human oral epithelial cell line HOEC and OSCC cell line HSC-4,CAL-27 and SCC-15,respectively.SCC-15 cells were divided into 7 groups of Ct(control,A),si-NC(B),si-CircBICD2(C),miR-NC(D),miR-218-5p(E),si-CircBICD2+anti-NC(F)and si-CircBICD2+anti-miR-218-5p(G).qRT-PCR was ap-plied to detect the expression of CircBICD2 and miR-218-5p in the cells;CCK-8 assay and plate cloning assay were applied to detect the cell proliferation;flow cytometry was applied to detect cell apoptosis;Western blot was applied to detect the protein expressions of RhoA,E-cadherin,Vimentin and N-cadherin;dual luciferase was applied to verify the relationship between CircBICD2 and miR-218-5p,miR-218-5p and RhoA,respectively.Results:In OSCC tissues and cells,CircBICD2 and RhoA proteins were highly ex-pressed,miR-218-5p was lowly expressed.In SCC-15 cells,the expression of CircBICD2 and RhoA protein was the highest,and the expression of miR-218-5p was the lowest(P＜0.05),SCC-15 cells in the 7 groups showed that,compared with group B,the expres-sion of CircBICD2 and RhoA in group C was decreased,and the expression of miR-218-5p was increased(P＜0.05);compared with group D,in group E RhoA protein expression level was decreased,and the miR-218-5p expression level was increased(P＜0.05);compared with group C and group F,the expression of miR-218-5p decreased in group G,and the expression of RhoA protein in-creased(P＜0.05).Down-regulation of CircBICD2 or over-expression of miR-218-5p inhibited SCC-15 cell proliferation and EMT,and induced cell apoptosis;down-regulation of miR-218-5p attenuated the inhibition of SCC-15 cell proliferation and EMT,the cell apoptosis was promoted by silencing CircBICD2.Cir-cBICD2 targeted the miR-218-5p/RhoA axis.Conclusion:Silencing CircBICD2 may inhibit RhoA expression by up-regulating miR-218-5p,inhibits SCC-15 cell proliferation and EMT,and induces cell apoptosis.