Abstract: The short carbon fiber (C_f) reinforced hydroxyapatite (HA)/poly (methyl methacrylate) (PMMA) bio-composites were prepared by an in-situ processing and solution co-mixing process. The structures and fracture surface morphologies of as-used materials were characterized using XRD，FTIR spectra，SEM and EDS analysis.The mechanical properties of the C_f-HA/ PMMA composites were tested by a universal testing machine. The results reveal that short C_f and HA nano-particles are uniformly dispersed in the PMMA matrix. The as-prepared C_f-HA/PMMA composites have excellent mechanical properties. With the increase of the content，the flexural strength and flexural modulus of C_f-HA/PMMA composites firstly increase to the maximum and then decrease. When C_f and HA mass fractions are 4% and 2%，respectively，the flexural strength and modulus reach the maximum values of 97.41MPa and 3.06 GPa. The SEM fracture morphologies of C_f-HA/ PMMA composites indicate that with the increase of C_f mass fraction to 6%，the aggregation of C_f in the PMMA matrix is found.