Objectives To explore the effect and mechanism of calycosin promoting PC-3 cells apoptosis.Methods MTT assay was applied to evaluate the effect of calycosininhibitting the PC -3 cells proliferation rate after treated with different final concentrations:0,25,50,100,200μmol/L,solvent control (DMSO) for 48h.Flow cytometric analysis was used to evaluate the apoptosis of PC -3 cells treated with 0,25,50,100,200μmol/L calycosin for 48 h.The expression levels of Akt,p -Akt,Bax,Bcl-2 and Caspase-3 protein in 0μmol/L group,200μ mol/L calycosin group,200μmol/L calycosin + PI3K specific inhibitor(Wortmannin) group were detected by Western Blot.Results MTT assay showed that calycosinwas able to inhibit the PC-3 cells proliferation in a dose dependent manner (P ＜ 0.05);Flow cytometry experiments displayed the apoptosis rate of PC-3 cells after treated with 0,25,50,100,200μmol/L calycosin for 48h were (0.1± 0.04) ％,(6.8 ±0.6)％,(9.2 ±0.2)％,(11.5 ±0.27)％,(59.2 ±0.36)％ (P ＜0.05).Western blot experiment showed that the expression level of p-Akt and Bcl-2 in the 200 μmol/L calycosin group decreased compared with the 0μmol/L group (P ＜ 0.05),when adding Wortmanninin in the 200μmol/L calycosin group,this result was strengthened again.Compared with the 0μmol/L group,the expression level of Bax and Caspase-3 in the 200 μmol/L calycosin group increased (P ＜ 0.05),when adding Wortmanninin in the 200μmol/L calycosin group,this result was strengthened again.Conclusions Calycosin is able to inhibit the PC-3 cells proliferation and induce its apoptosis.The relative mechanisms are down-regulating of the PI3K/Akt signaling pathway and activation of the mitochondrion pathway of apoptosis.