Abstract: Objective To investigate the effects of retinoic acid (RA) on the expression of Cx43 and its gap junction intercellular communication function in testicular cancer cells. Methods Cultured testicular cancer cells I-10 were treated with different concentration of RA (2.5,5.0,10.0 μmol/L). The expression of Cx43 in I-10 cells was detected by Western blot, and the distribution and location of Cx43 on cellular membrane was studied with immunofluorescence assay. Parachute assay was used to detect the function of gap junction intercellular communication composed of Cx43 in I-10 cells. Results RA (2.5, 5.0, 10.0 μmol/L) markedly increased the expression of Cx43 in I-10 cells, the enhancement ratios were 43.14%±2.1%, 58.09%±1.8%, 143.13%±1.6%, respectively. The result of immunofluorescence assay showed that RA (2.5, 5.0, 10.0 μmol/L) obviously increased the level of Cx43 located on the cellular membrane of I-10 cells. The result of parachute assay demonstrated that RA (2.5,5.0,10.0 μmol/L) could enhance the intercellular dye coupling through gap junction, the enhancement ratios were 26.1%±2.3%, 63.3%±1.6%, 140.5%±3.4%, respectively. Conclusion RA could enhance the gap junction intercellular communication by increasing the expression of Cx43 in I-10 cells.