To investigate the effect of Guttiferone K(GUTK)，a polycyclic polyprenylated acylphloroglucinol(PPAPs)compound isolated from Garcinia yunnanensis，on inhibiting reactivation of quiescent prostate cancer LNCaP cells.Methods：LNCaP cells were induced into a quiescent stage by seven days of serum withdrawal and stimulated cell cycle re-entry with or without GUTK by serum restoration.Ki-67 protein expression level was detected by Immunocytochemistry.Flow cytometry of Propidium iodide(PI)staining and EdU Incorporation assay were used to analyze cell cycle phase distribution.Protein levels of Cyclin D1/3、CDK4/6 and E2F1 were detected by Western blotting.Results：GUTK dose-dependently blocked the re-proliferation and S phase re-entry of quiescent LNCaP cells.GUTK decreased the Cyclin D1/3、CDK4/6 and E2F1 protein levels during quiescent LNCaP cell cycle re-entry.Conclusion：GUTK，a compound isolated from Garcinia yunnanensis，has the potential to inhibit cancer progression and prevent cancer recurrence by suppressing cell cycle re-entry of quiescent prostate cancer LNCaP cells.