Objective To investigate the effects of miRNA overexpression on drug resistance of cis-diamminedichloroplatinum (CDDP) resistant gastric cancer cell line BGC-823/CDDP. Methods Human genomic DNA was extracted, PCR primers targeting human miRNA765 were designed, and gene sequence containing miRNA765 precursor was amplified by PCR and cloned into an eukaryotic expression vector to construct a recombinant miRNA expression vector. BGC823/CDDP cells were transfected with the recombinant plasmid using cationic liposome. Forty-eight hours after transfection, the relative contents of miRNA765 and cytokine-induced apoptosis inhibitor 1 (CIAPIN1) protein in cells were determined by Real-Time PCR and Western blotting. Forty-eight hours after transfection, the cells were treated with different concentrations of CDDP. Twenty-four and forty-eight hours later, cell viability was detected using MTT assay, and 50% concentration of inhibition (IC50) of the cells to CDDP was calculated. BGC-823/CDDP cells of gene intervention were treated with CDDP at a final concentration of 1 μg/mL, and double staining method was used to detect the cell apoptosis rate. Results The relative expression of miRNA765 in BGC-823/CDDP cells was significantly lower than that in parental cell line BGC-823 (P<0.01), and the relative expression of CIAPIN1 protein in BGC823/CDDP cells was significantly higher than that of parental cell line (P<0.01). The overexpression of miRNA765 significantly inhibited the expression of CIAPIN1 protein in BGC-823/CDDP cells. Forty-eight hours after transfection, the expression of CIAPIN1 protein was significantly lower than that of the untransfected group (P<0.01). The overexpression of miRNA765 significantly reduced the drug resistance of BGC-823/CDDP cells, and 48-hour IC50 value was reduced from (18.27±3.92) μg/mL to (1.50±0.43) μg/mL (P<0.05). Forty-eight hours after transfection, the apoptosis rate of BGC-823/CDDP cells was significantly increased from (10.1±1.7)% to (53.4±7.9)%（P＜0.01）. Conclusion The overexpression of miRNA765 may significantly reduce the drug resistance of resistant gastric carcinoma BGC-823/CDDP cells.