Objective To study the effects on MCF-7 breast cancer cells with combination of tamoxifen（TAM） and antisense oligonucleotide （ASODN） targeting survivin mRNA. Methods MCF-7 breast cancer cells were treated with a 20 mer ASODN targeting survivin mRNA and TAM, which were divided into three groups: TAM group (treated by TAM only), ASODN group (by ASODN only), and TAM+ASODN combined group (by TAM+ASODN combination). The growth inhibition of MCF-7 cells, the changes of cell cycles and apoptotic rate, the positive rate of survivin mRNA expression, and the activity of caspase-3 were tested by MTT, flow cytometry, hybridization in situ, and spectrophotometric method, respectively.Results The rate of growth inhibition of MCF-7 cells in the TAM+ASODN combined group was (62.26±3.92)%, which was significantly higher than that in the TAM group 〔(42.30±6.63)%〕 or ASODN group 〔(54.77±9.99)%〕, Plt;0.05. The apoptotic rate of MCF-7 cells was (28.08±4.32)% in the TAM+ASODN combined group, which was significantly higher than that in the TAM group 〔(18.94±4.01)%〕 or ASODN group 〔(21.12±3.95)%〕, Plt;0.01. The effect of arresting MCF-7 cells in G0/G1 phase in the TAM+ASODN combined group was ber than that in the TAM or ASODN group (Plt;0.05, Plt;0.01). The positive rate of survivin mRNA in the TAM+ASODN combined group was (13.38±3.45)%, which was significantly lower than that in the TAM group 〔(39.67±7.42)%〕 or ASODN group 〔(27.50±5.80)%〕, Plt;0.01. The activity of caspase-3 in the TAM+ASODN combined group （0.93±0.13） was significantly higher than that in the TAM group (0.50±0.09) or ASODN group (0.64±0.08), Plt;0.01. Conclusion The ASODN targeting survivin mRNA can promote the apoptosis of MCF-7 breast cancer cells, and make MCF-7 cells more sensitive to tamoxifen.