Abstract: Achyranthes bidentata polysaccharide sulfate (ABPS) was a sulfated derivate derived from Achyranthes bidentata polysaccharide (ABP) which was isolated and identified from Chinese herb Achyranthes bidentata. The anti human immunodeficiency virus type 1 (HIV-1) activities were studied in vitro and in vivo. ABPS was found to inhibit HIV-1 reverse transcriptase and integrase with the 50% inhibiting concentration (IC₅₀) of (2.948±0.556) μmol·L^-1 and (0.155±0.030) μmol·L^-1, respectively, but the parent compound ABP was not effective. ABPS inhibited HIV-1 P24 antigen with IC₅₀ of (0.082±0.044) μmol·L^-1 and selective index (SI) of >(358±148) in MT-4 cell cultures acutely infected with HIV-1 IIIB virus, and with IC₅₀ of (11.80±5.90) μmol·L^-1 and SI of >(24.2±12.1) in PBMC cell cultures acutely infected with clinical isolated zidovudine resistant HIV-1 virus, but there was no activity even at its concentration of 500 μmol·L^-1 in latent infection of H9/ HIV-1 IIIB cell cultures. 5% sera taken from rats after intraperitoneal injection from rats with ABPS 125 mg·kg^-1 once or mice with 3 mg·kg^-1 qd for 20 days effectively inhibited HIV-1 P24 in MT-4 cell cultures, but those had no inhibitory effect when given orally. The results suggested that ABPS is a promising HIV-1 inhibitor, active on HIV-1 reverse transcriptase, integrase in vitro and HIV-1 P24 antigens in cell cultures, it was well absorbed by intraperitoneal injection but poor in oral bioavailability. It warrants further study.