Nano-bioactive glass (NBG), with a composition of 35CaO-60SiO2-5P2O5 (mol%), was prepared via sol-gel method and freeze-dried technique using polyethylene glycol (PEG) as dispersant. The optimal sintering temperature was determined via TG/DTA, and NBG was characterized by FTIR, TEM and XRD. XRD pattern of NBG calcined at 650 ℃ in air confirmed that the calcined glass generally existed in amorphous state. The particle size of NBG prepared with PEG200 was >100 nm. The particle size of NBG prepared with PEG10 000 was 50～80 nm, and the shape of NBG was hollow spherical. The shape of NBG with PEG 20 000 was a long strip (10×100 nm). With increasing of PEG concentration, the particle size decreased.