The nano-powder of Al2O3-SiO2-CaF2 bio-glass was prepared by the homo-precipitation method with some inorganic salts containing Al3+, Ca2+, Na+, F-, SiO3 2+, Cl- as starting-reagents. The composition and characteristics of the powders were studied with XRD, EDAX, TEM and DTA. The results indicate that the prepared powder belongs to amorphous compounds containing Al, Ca, Si, O and F atoms and the size of particle is in the range of 30 ~ 70 nm. Adding citric acid and the well-controlled desiccation process can slightly improve the dispersing effect of the powders; the mixture ratio of the reagents rarely affects the characteristic of powder. The crystal phase CaF2 was precipitated firstly from the amorphous structure when the temperature is above 600°C, with the temperature rising, Al2SiO5 and Al4.4Si1.2O9.5 etc. crystal phases were precipitated sequentially.