Objective The aims of this study were to investigate the expression of microRNA-30a(miR-30a)in human bladder cancer cell lines and their effects on the proliferation,apoptosis and migration of human bladder cancer cells.Methods The expression levels of miR-30a in bladder cancer cell lines(5637 and T24)and bladder epithelial immortalized cells(SV-HUC-1)were detected by real-time quantitative PCR(qRT-PCR).The expression of miR-30a was up-regulated or down-regulated by T24 cells transfected with miR-30a mimic or 5637 cells transfected with miR-30a inhibitors and controls using NC mimic or NC inhibitor.The effects of miR-30a expression on the proliferation,apoptosis and invasion of bladder cancer cells were investigated by flow cytometry,MTT and Transwell assays.Results The expression level of miR-30a in two bladder cancer T24 and 5637 cell lines was significantly lower than that in normal bladder SV-HUC-1 cell line(P<0.05),and the expression level of miR-30a was lower in the high degree of malignancy in bladder cancer T24 cells than that in malignant degree of relatively low 5637 cells.After 72h transfection,the values of optical density(OD)in the miR-30a mimic group(0.83±0.09)was significantly lower than that in NC mimic group(1.21±0.12)in T24 cells(P<0.01).The OD values of miR-30a inhibitor group(1.28±0.14)was significantly lower than that in the NC inhibitor group(1.09±0.14)in 5637 cells(P<0.01).The apoptotic rate of miR-30a mimic group in T24 cells(21.27±2.42)% was significantly higher than that in the NC mimic group(10.61±1.29)%(P<0.01).The apoptotic rate of the miR-30a inhibitor group in 5637 cells(6.78±2.57)% was significantly lower than that in the NC mimic group(13.42±1.40)%(P<0.01).The number of transmembrane cells in miR-30a mimic group in T24 cells(183.57±16.61)was significantly lower than that in NC mimic group(465.80±9.20)(P<0.01).The number of transmembrane cells in the miR-30a inhibitor group in 5637 cells(581.25±11.02)was significantly lower than that in NC mimic group(397.13±7.57)(P<0.01).Conclusion Up-regulation of miR-30a can inhibit the proliferation of bladder cancer cells,promote cell apoptosis and reduce the ability of migration and invasion in bladder cancer cells.The low expression of miR-30a in bladder cancer cells may be related to the development and metastasis in bladder cancer.