Aim: To investigate curcumin (diferuloylmethane)-induced apoptosis and its molecular mechanism of action in B-NHL cell line Raji cells. Methodology: Raji cells were cultured in RPMI-1640 medium and treated with curcumin in different concentrations (6.25, 12.5, 25.0, 50.0 and 100.0 µmol/litre). 3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium assay was used to detect growth inhibition and Hoechst 33258 staining was used to detect apoptosis. Immunocytochemistry and Western blot were used to detect the expressions of histone deacetylase 1, 3 and 8 (HDAC1, HDAC3 and HDAC8) and acetylated histone H4 (Ac-histone H4) protein. Results: Curcumin inhibited the proliferation of B-NHL cell line Raji cells, with a 36-h IC₅₀ value of 24.1±2.0 mol/litre. Hoechst 33258 staining showed that curcumin could induce Raji cell apoptosis. The expression levels of HDAC1, HDAC3 and HDAC8 proteins were downregulated following curcumin treatment in Raji cells, whereas Ac-histone H4 protein expression was upregulated after treatment with curcumin. Conclusion: Curcumin, as a new member of the histone deacetylase inhibitors, can inhibit the expression of class I HDACs (HDAC1, HDAC3 and HDAC8), and can increase the expression of Ac-histone H4 in Raji cells. Curcumin plays an important role in regulating B-NHL cell line Raji cell proliferation and apoptosis.