Objective To explore the effects of 2,3,5,4'-tetrahydroxy stilbene-2-β-D-glycoside(TSG)on the over-expression and aggregation of α-synuclein in vitro.Methods TSG in different concentrations was incubated with α-synuclein transgenic COS-7 cells for 24 h.The cell viability was measured by MTT method.The expression of α-synuclein protein was determined by immunocytochemistry and Western blotting method.Results Incubation of TSG at the range of 12.5-200.0 μmol/L with α-synuclein transgenic COS-7 cells for 24 h did not influence cell viability,but a dose-dependently inhibition for the over-expression of α-synuclein protein could be observed in the tests of immunocytochemistry and Western blotting.Conclusion TSG can inhibit the over-expression of α-synuclein protein in COS-7 cells in vitro.