Objective To establish a gastric cancer cell line with stable Drosha silenced and explore the effect of Drosha on the chemosensitivity of gastric cancer cells to epirubicin. Methods Interfering sequences targeting Drosha were designed and inserted into the lentiviral vectors, which were used to transfect MGC-803 cells. The level of Drosha mRNA was detected by quantitative real-time PCR; Drosha protein was detected by Western blotting; MTT assay was performed to test the 50% inhibitory concentration (IC50) of epirubicin agaisnt wide-type MGC-803 cells. After the treatment with IC50 epirubicin, the apoptosis rate of each cell group was determined by flow cytometry; the expressions of apoptosis-related proteins caspase-3, caspase-9, Bax, Bcl-2 were assessed by Western blotting. Results The gastric cancer MGC-803 cells with stable Drosha silenced were successfully established, and the levels of Drosha mRNA and protein were reduced. After the cells were treated with 0.5 mg/L(IC50) epirubicin, the apoptosis rate of MGC-803 cells was raised, the protein expressions of caspase-3 , caspase-9 and Bax were significantly upregulated and Bcl-2 was downregulated. Conclusion The silence of Drosha expression can promote the sensitivity of gastric cancer to epirubicin.