Purpose: The objective of the present study was to determine the capability of electrospun silk fibroin as a biomaterial template for bone formation when mixed with nano-hydoxyapatite in vivo. Materials and Methods: Ten New Zealand white rabbits were used for this study and bilateral round shaped defects were formed in the parietal bone (diameter: 8.0 mm). The electrospun silk fibroin was coated by nano-hydroxyapatite and grafted into the right parietal bone (experimental group). The left side (control group) did not receive a graft. The animals were sacrificed at 6 weeks and 12 weeks, humanly. The microcomputerized tomogram (${mu}CT$) was taken for each specimen. Subsequently, they were undergone decalcification and stained for the histological analysis. Results: The average value of all measured variables was higher in the experimental group than in the control at 6 weeks after the operation. BMC in the experimental group at 6 weeks after operation was $48.94{pm}19.25$ and that in the control was $26.17{pm}16.40$ (P = 0.027). BMD in the experimental group at 6 weeks after operation was $324.59{pm}165.24$ and that in the control was $173.03{pm}120.30$ (P = 0.044). TMC in the experimental group at 6 weeks after operation was $19.50{pm}6.00$ and that in the control was $10.52{pm}6.20$ (P = 0.011). TMD in the experimental group at 6 weeks after operation was $508.88{pm}297.57$ and that in the control was $273.54{pm}175.91$ (P = 0.06). Gross image of both groups showed higher calcification area at 12 weeks than them in 6 weeks. The average value of ${mu}CT$ analysis was higher at 12 weeks than that in 6 weeks in both groups. BMC in the experimental group at 12 weeks after operation was $51.21{pm}8.81$ and that in the control was $33.47{pm}11.13$ (P = 0.010). BMD in the experimental group at 12 weeks after operation was $323.39{pm}21.54$ and that in the control was $197.75{pm}76.23$ (P = 0.012). TMC in the experimental group at 12 weeks after operation was $21.44{pm}5.30$ and that in the control was $13.31{pm}4.17$ (P = 0.008). TMD in the experimental group at 12 weeks after operation was $524.47{pm}19.37$ and that in the control was $299.60{pm}136.20$ (P = 0.016). Conclusion: The rabbit calvarial defect could be successfully repaired by electrospun silk nano-fiber combined with nano-hydroxyapatite.