This study is aimed to evaluate the role of Platelet Rich Plasma PRP on osteogensis in periosteal distraction. The sample consisted of 12 rabbits from local spices. The sample divided equally into two groups, titanium mesh with holes was used in to elevate the periosteum and the space between the surface of bone and the mesh was filled with collagen sponge, in the test group the sponge was injected with PRP. The rabbits were killed after eight weeks after operation and the samples were prepared for histological study. The histological study of specimens of control group showed formation of small island of osteoid with large areas of connective tissue. While, in test group there was an increasing in bone formation in form of wide area of woven bone and decreasing in connective tissue. We conclude that application of Platelet Rich Plasma PRP lead to improvement in bone formation in periosteal distraction.