Objective: To investigate the let-7a microRNA (miRNA) expression in cholangiocarcinoma tissue and its significance. Methods: The let-7a expressions in tissues of cholangiocarcinoma and normal bile duct specimens were determined by Real-time PCR technique. The cholangiocarcinoma HuCCT-1 cells were divided into let-7a overexpression group (transfected with let-7a mimics), negative control group (transfected with negative control sequence) and blank control group (without any transfection), and then the let-7a expression, apoptosis and cell cycle in each group of cells were determined by Real-time PCR and flow cytometer, respectively. Results: The let-7a expression was significantly down-regulated in cholangiocarcinoma tissue than that in normal bile duct tissue (P<0.01). Both let-7a expression and apoptotic rate in cells of let-7a overexpression group were all significantly increased compared with blank control group (both P<0.01), while no such differences were noted between the negative control group and blank control group (both P>0.05). The difference in cell cycle showed no statistical significance among groups (P>0.05). Conclusion: The let-7a expression is down-regulated in cholangiocarcinoma tissue and inhibits cell apoptosis and, may thereby promote the occurrence and development of cholangiocarcinoma.