The purpose of this work is to investigate the effect of heating treatment on the structure and bioactivity of the 58S bio-glass. Phase composition analyzed by XRD and FTIR techniques indicates that the sample heated at 700 o C produced an amorphous state while the ones heated at 900 and especially 1100 o C resulted in two crystalline phases of CaSiO3 and Ca3(PO4)2. The in vitro experiment was carried out for the 58S bio-glass sample heated at 1100 o C by soaking the powder sample in the SBF solution at different times. The XRD result confirms that the heating treatment inhibited the bioactivity through the slower formation of hydroxyapatite layer on the surface of sample after immersion. The specific area and surface morphology of heating sample were also evaluated by BET and SEM measurements.