Aim To study the action of ATP binding cassette transporter A1 (ABCA1) on cholesterol efflux in THP 1 macrophage derived foam cell. Methods After exposure of the cultured THP 1 macrophage derived foam cell to 22(R) hydroxycholesterol and 4,4' diisothiocyanostilbene 2,2' disulfonic acid (DIDS) at different time, cholesterol efflux and ABCA1 protein level were determined by FJ 2107P type liquid scintillator and flow cytometer, respectively. Results 22(R) hydroxycholesterol increased cholesterol efflux in THP 1 macrophage derived foam cell with time dependent pattern and DIDS inhibited cholesterol efflux in THP 1 macrophage derived foam cell with time dependent pattern; flow cytometer showed that exposure of the cultured THP 1 macrophage derived foam cell to 22(R) hydroxycholesterol and DIDS at different time, resulted in increase and decrease in the expression of ABCA1 protein in THP 1 macrophage derived foam cell with time dependent pattern, respectively. Conclusion ABCA1 play an important role in cholesterol efflux in THP 1 macrophage derived foam cell.