Abstract: Objective To evaluate the impact of RNA interfering coiled-coil domain-containing 34（CCDC34）on the proliferation， apoptosis， colony formation and invasion of human bladder cancer cell lines. Methods Bladder cancer 5637 cells were infected with lentivirus-mediated CCDC34 negative control siRNA（negative control group）and CCDC34 siRNA（CCDC34siRNA group）respectively. Fluorescence microscopy was used to observe the infection efficiency. qPCR and Western blotting were used to confirm the interfering efficiency of CCDC34. The cell proliferation，apoptosis，colony formation and invasion ability were analyzed by BrdU incorporation assay，flow cytometry，lowdensity cell colony formation and transwell experiments. Results The lentivirus infection efficiency was above 85％ for both CCDC34-siRNA group and negative control group. The mRNA expression of CCDC34siRNA group was greatly reduced compared with negative control group（1.00±0.06 vs. 0.16±0.01，P＜0.01），as well as the expression of CCDC-34 protein. Compared with negative control group，cell proliferation was significantly inhibited in the CCDC34-siRNA group （P＜0.05）；the percentage of 5637 cells in apoptosis phase was also significantly increased in the CCDC34-siRNA group［（28.09±0.39）％ vs.（9.50±0.01）％，P＜0.01）］. The number of colonies in CCDC34-siRNA group was statistically less than that in negative control group（22±4 vs. 310±5，P＜0.01）. The cell invasion rate of CCDC34-siRNA group was significantly lower than that of negative control group（0.53±0.03 vs.2.58±0.10，P＜0.01）. Conclusion Down-regulation of CCDC34 in bladder cancer cell line 5637 via lentivirusmediated siRNA can inhibit the cell proliferation，colony formation and invasion. CCDC34 may serve as a biomarker or even a therapeutic target for bladder cancer.