Purpose The purpose of this study is to evaluation of effect on bone formation of PRP and fibrin sealant with deproteinized bovine bone(Bio-Oss) grafts on rabbit cranial defect. Material and Methods Twelve rabbits were used as experimental animal Two equal 9mm diameter cranial bone defects were created in each rabbit and immediately grafted with Bio-Oss only, Bio-Oss and PRP, and Bio-Oss and Fibrin sealant. Rabbits were sacrificed at 4 and 8 week. The defects were evaluated by histomorphometric analysis. Results Kruskal-Wallis tests were performed comparing new bone formation via histomorphometric analysis. No statistically significant difference of new bone formation was found between Bio-Oss only, Bio-Oss and PRP, and Bio-Oss and fibrin sealant at 4 and 8 weeks (P>0.05). Conclusion This study fails to find a stimulatory effect of PRP and Fibrin sealant on New bone formation of Bio-Oss grafts by histomorphometric analyses.