We developed a novel BMP2-mimicking peptide P28, which possesses two distinct special structural elements -- seven repetitive aspartic acids and phosphorylated serine designed to promote affinity to hydroxyapatite as well as nucleation of apatite crystallization and mineralization. In this work, we systematically studied the osteogenic inductivity of P28 in vitro and in vivo in comparison with BMP2. We confirmed its effects on proliferation, recruitment, and osteogenic differentiation of MC3T3-E1 cells in vitro. Furthermore, we loaded P28 into a biomimetic bone composite nanohydroxyapatite/collagen/poly(l-lactide) (nHAC/PLA) and evaluated its ability to promote bone regeneration in vivo using a rabbit femoral condyle defect model. The micro-CT reconstruction and quantification analysis and the histological analysis indicated that P28/nHAC/PLA bone composite was capable of repairing bone defects.