Abstract: The mechanical properties of poly(DL lactide)/hydroxyapatite composites was improved by treating the surface of hydroxyapatite reinforcing particles with silane agent(A 174). SEM observation indicated that the surface modified HA microparticles were uniformly distributed within PDLLA matrix, and showed a more intimate contact with the polymer matrix than that in the case of unmodified filler particles. XPS proved the presence of O P Si bond between the interfacial bonding by using such method, and a new biodegradable bone bonding composite can be made.