Biphasic calcium phosphate (BCP) powders were prepared by hydrolyzation proc-ess and surface-modified by directly grafted L-lactide (LLA) onto the surface of BCP through a chemical linkage. The grafting ratio of organic groups was 9 wt%. After surface modification, the surface of BCP powders was covered by the lamella-shaped crystal. Poly (L-lactide) was mixed with BCP to form the BCP/PLLA biocomposite. Modified BCP (mBCP) particles could be uniformly dis-persed in PLLA matrix. The compressive strength of the mBCP/PLLA composite is 115 MPa, 28% higher than that of unmodified-BCP/PLLA composite. The improved mechanical strength is attributed to the enhanced adhesion between the inorganic BCP filler and the organic PLLA matrix.