Objective: To investigate the effect of up-regulating miRNA-34a expression on growth of human colon cancer cells in vitro. Methods: Human colon cancer HT-29 cells were transfected with artificially synthesized miRNA-34a mimics and negative control sequences respectively. After culture for various times, the cell proliferation was measured by MTT assay, the apoptosis was detected by flow cytometry, and the expression of SIRT1 mRNA and protein was detected by qRT-PCR and Western blot analysis, respectively. Results: Compared with HT-29 cells transfected with negative control sequences, the proliferation of HT-29 cells transfected with miRNA-34a mimics was significantly decreased after 48-h culture; the apoptosis rate was significantly increased, and both expressions of SIRT1 mRNA and protein were significantly down-regulated after 72-h culture, and all differences had statistical significance (all P<0.05). Conclusion: MiRNA-34a can influence the biological behaviors of colon cancer cells probably through regulating expression of its target gene SIRT1, and up-regulating miRNA-34a expression can inhibit the growth of colon cancer cells.