Objective To investigate the effect of cell death by HIV-1 infection on gene 90K/Mac-2BP by RNA interference (RNAi) in U937 cell line. Methods We used human monocyte-macrophage cell line U937 as the cell model. Cells were infected by HIV-1 (R5-tropic) 5 days, and then stained by PE-Annexin V and PerCP-7-AAD. 90K/Mac-2BP in U937 cell line was knocked down, and these cells were infected by HIV-1 for 5 days. Then, cells were stained by PE-AnnexinV and PerCP-7-AAD. Apoptosis were examined upon flow cytometry. Results The percentages of Annexin V⁺ cells without 90K/Mac-2BP knock-down were (16.27±0.30)% by HIV-1 infection. The percentages of them with 90K/Mac-2BP knock-down were (31.26±0.35)%, (25.76±0.30)%, (23.69±0.33)% respectively. The increase of cell apoptosis rate for HIV-1-infected U937 cells by 90K/Mac-2BP siRNA transfection was significantly greater than that for HIV-1-infected untreated cells (P<0.01). Conclusion The apoptosis of HIV-1-infected U937 cells was regulated by the expression of 90K/Mac-2BP.