The formation and thermal properties of the $BaO_2$ and $TiO_2$ mixtures were prepared by mechanical alloying method was investigated by X-ray diffractometry (XRD), scanning electron microscopy (SEM), and thermogravimetric/differential thermal analysis (TG/DTA). The rotating speed of 750 rpm shows more effects on the formation of $BaTiO_3$ single phase. The internal strain calculated using Williamson-Hall method was $4.27{ imes}10^{-3}$ for the mixture milled for 300 min, the crystallite size was calculated using the Scherrer method decreased with milling time. The $BaTiO_3$ crystal improved crystallinity was formed by thermal annealing at a temperature of $600^{circ}C$ for 1 h for the mixture milled for 300 min.