The aim of this study was to investigate and compare the effect of the Nano Hydroxyapatite (NHA) and Nano Hydroxyapatite doped by magnesium (NHA-Mg) on healing of fracture in dogs. Twenty-seven adult dogs of both sexes aging between 2-3years old were randomly assigned into three groups. Group one (control group), group two (NHA group), and group three (NHA-Mg). An experimental model of diaphyseal complete radial fracture was surgically created by gegli saw. The fractured radius was fixed by extra-medullary 6-hole dynamic compression plate (6 hole DCP), with addition of the previously mentioned materials to fill the radial fracture defect in the corresponding groups. Data of clinical observation, plain radiography, computed tomography (CT) and histopathological examination and scoring were recorded on 45, 75, 90 days after induction of fracture. The dogs of all groups achieved the full bearing weight and stance 5 days postoperatively. The radiographs admit little knowledge about the healing scoring rather than the CT which declares that N HA-Mg was improve the filling of fracture defect. The histopathological examination and scoring revealed that NHA-Mg was superior HA alone in fracture healing. Data of the present work showed that nano hydroxyapatite doped by (0.007mol) magnesium concentration allows complete calcification and healing of the fractured radius during the experimental time frame.