Objective: To investigate the effect of glycyrrhizin on cell growth in human prostate cancer cell line PC3 and explore the underlying mechanisms. Methods: CCK-8 assay was applied to analyze the inhibition rate of PC3 cells after treated with different concentrations (5, 10, 20, 40 or 80 μmol/L) glycyrrhizin for different times (6, 12, 24 or 48 h). Cell cycle distribution was determined by flow cytometry. Moreover, the protein expressions of cyclin D1, P21, p-PI3K, PI3K, p-AKT and AKT were detected using Western blot. Results: CCK-8 assay data showed that glycyrrhizin inhibited PC3 cell growth in a concentration-dependent and time-dependent manner. When the concentration reaches 40 μmol/L, the inhibition reaches its maximum. Glycyrrhizin treatment was found to inhibit cell cycle transition from G0/G1 to S phase, which was accompanied with decreased cyclin D1 expression and increased P21 expression. Moreover, the phosphorylation of PI3K and AKT were significantly decreased after glycyrrhizin treatment, whereas the expressions of PI3K and AKT remained unchanged. Conclusion: Glycyrrhizin inhibits cell cycle transition by regulating expression of cyclin D1 and P21 via inactivation of PI3K/AKT signaling pathway, and thereby attenuating PC3 cell growth.