BaO.6Fe2O3 magnet materials have been successfully synthesized by co-precipitation method from the precursor solution with pH = 9 and pH = 12. The characterization was done by means of X-Ray Diffractometer (XRD), Vibrating Sample Magnetometer (VSM), Differential Thermal Analyses (DTA)/Thermal GravimetricAnalysis (TGA), Scanning ElectronMicroscope (SEM) and Transmission Electron Microscope (TEM). The results ofmagnetic properties measurement using VSM showed that sintered BaO.6Fe2O3 at 800 oC from precursor with pH = 12 has highest magnetic coercivity Hci = 5.6 kOe. High magnetic coercivity is likely due to the very fine crystallites size approach single-domain. This is supported by SEM and TEM observations show that the length of the BaO.6Fe2O3 particle size is about 50-150 nm after sintering process at 800 oC. Thus BaO.6Fe2O3 materials obtained from this activity can be classified as the high-energy magnet hexaferrite which has a great potential to be used as a component of energy generation.