Abstract: Objective To explore the effect of berberine on the proliferation and apoptosis of melanoma B16 cells. Methods The CCK-8 method was used to detect cell proliferation viability. Cell cycle was detected by flow cytometry. The programmed cell death 4(PDCD4)gene was knocked down by liposome transfection of siRNA. Quantitative real-time reverse transcription polymerase chain reaction(qRT-PCR)was used to identify knockout condition. Cell apoptosis was detected by flow cytometry. Expressions of PDCD4, proliferation-associated and apoptosis-associated proteins were detected by Western-blotting. Results Berberine was able to inhibit the proliferation viability of melanoma B16 cells and arrest cell cycle at G₀/G₁ phase.PDCD4 was the key gene for berberine to inhibit proliferation and promote apoptosis of melanoma B16 cells. Berberine treatment was able to increase the expression levels of PDCD4, Cleaved Caspase-3 and Bcl-2 associated protein X(Bax)as well as decrease expression levels of Ki-67 and Bcl-2. The effect of berberine on Ki-67, Bcl-2, Bax and Cleaved Caspase-3 of melanoma B16 cells was weakened by knocking out PDCD4. Conclusion Berberine can inhibit proliferation and promote apoptosis of melanoma B16 cells by up-regulating PDCD4.