A large size bone defect is a challenging problem in orthopedic. This trial focuses on investigating the effects of Hydroxyapatite Nano gel as filling materials for accelerating the healing of repaired tibial bone defects in dogs.  The experiment included 18 healthy dogs which was randomized divided into two equal groups, 9 of each. The experimental bone defect was created at (2.5 by 0.7cm ) in both groups. In the control group, the same bone piece is reimplanted at the experiment defect and fixed with Cerclage wire. In the second group, a deproteinized lamb rib at (2.4 by 0.6cm) was used to repair the bone defect, and the graft segment was fixed with Cerclage wire, and the repaired defect was supported with hydroxyapatite Nano gel. The animals were monitored clinically, grossly and radiologically on days 14, 30 and 60. The defect completely healed with no apparent changes on day 60 post-operatively. Radiographically, in the control group on day 60, there was a faint lucent line around the fixated bone segment with minimal cortical thickening and irregularities denoting late chronic periosteal reaction and callus formation and near complete healing with the surrounding area whereas in the treatment group, the callus formation was superior in comparison with control group and there are some cortical irregularities denoting chronic periosteal reaction. We demonstrate that using hydroxyapatite nano gel as an additive to the defective bone fills the voids, accelerates the healing process. Radiological analysis showed superior healing and callus formation in hydroxyapatite nano gel group with xenobone graft.