Abstract： Objective To investigate the in vitro effects of tea polyphenols (TP) on proliferation and cell cycle of human acute promyelocytic leukemia cell line HL-60. Methods The in vitro effects of TP on proliferation of HL-60 cells were analyzed by MTT colorimetric assay. The morphologic changes of HL-60 cells after TP treatment were observed by HE staining and immunofluorescence staining, and flow cytometry was used to examine the cell apoptosis rate and cell cycle. Results ①The result of MTT colormetric assay revealed that TP inhibited the proliferation of HL-60 cells in dose- and time-dependent manner within a certain range of dosage (P＜0.05). With 400 mg/L or 800 mg/L TP, the 48 h inhibition rate of the HL-60 cells was (58.90± 1.19) ％ and (72.57±0.70) ％, respectively. ②By using flow cytometry, a distinctive hypodiploid peak was observed in HL-60 cells cultured with TP, and the apoptosis rate was dose- and time-dependent.(3) HL-60 cells were arrested at S phase and the number of arrested cells was positively correlated with drug dose. The strongest blockage effect of TP was observed at 24 h. Conclusions Within a certain range of dosage, TP can inhibit the proliferation of HL-60 cells in dose- and time-dependent manner. TP can induce HL-60 cells apoptosis and block the cell cycle of HL-60 cells at S phase in vitro.