Abstract: Short carbon fiber (C_f) reinforced nano-hydroxyapatite (HA)-poly (methyl methacrylate) (PMMA) hybrid bio-composites were prepared by an in-situ processing and solution co-mixing process. The influences of surface modification of carbon fibers and nano-HA on the microstructures and mechanical properties of the C_f/HA-PMMA composites were investigated. The structures and fracture surface morphologies of nano-HA，carbon fiber and the composites were characterized by XRD，FTIR，XPS and SEM analyses. The flexural and compressive properties of the C_f/HA-PMMA composites were tested by a universal testing machine. The results show that the interfacial combination between the surface modified-HA particles by lecithin or pre-oxidized carbon fibers by nitric acid and PMMA matrix is evidently improved. Flexural properties of as-prepared C_f/HA-PMMA composites with the surface modification of HA particles and carbon fiber are obviously increased. Compared with the C_f/HA-PMMA composites using unmodified-HA particles and untreated-carbon fiber，the flexural strength，compressive strength and elastic modulus of modified composites increase 1.6 times，2 times and 4.3 times，respectively.