The effect and the mechanism of Lycium barbarum polysaccharide (LBP-X) on inhibiting the growth of human leukemia HL-60 cells were examined. LBP-X(20, 100, 500, 1000 mg/L) could inhibit the growth of HL-60 cells in dose-dependent manner and decrease the membrane fluidity of the cell. Agarose gel electrophoresis of DNA from the cells treated with LBP-X revealed a "DNA ladder" and positive TUNEL test. The results showed that the apoptosis of HL-60 cells induced by LBP-X maybe its important mechanism on anti-tumorgenesis.