In our previous study, we manufactured a composite poly(methyl methacrylate) (PMMA) bone cement by the impregnation of 3 wt.% of the surface-modified ultra high molecular weight polyethylene (UHMWPE) powder using methyl methacrylate (MMA)/xylene solution into conventional PMMA bone cement. However, the xylene which remains in the composite hybrid PMMA bone cement could induce chemical cellular necrosis due to its toxicity. In this study, various ratios of methyl methacrylate (MMA) (mL)/PMMA (g) solutions were used for the surface modification of UHMWPE powder to overcome xylene toxicity. The surface modification of UHMWPE powder had two steps; (1) UHMWPE powder was surface-treated by MMA/PMMA solution and (2) the surfacetreated UHMWPE powder was surface-precoated with polymerized PMMA from MMA monomer (polyMMA). The aims of the present study were to observe the surfaces of the surface-modified UHMWPE powder with MMA/ PMMA solution using a scanning electron microscope (SEM), to analyze the changes in the chemical composition of the surface-modified UHMWPE powder using a Fourier transform infrared-attenuated total reflectance (FTIRATR), to measure the tensile strengths for mechanical properties and the curing temperatures for thermal properties of the composite PMMA bone cements which were manufactured by the impregnation of 3 wt.% of the surfacemodified UHMWPE powder into conventional PMMA bone cement, and to sketch a possible interfacial bonding mechanism between the surface-treated UHMWPE powder and polyMMA. It was confirmed that the tensile strengths of the composite PMMA bone cements were similar to that (44.5 MPa) of conventional PMMA bone cement and a litter higher than that (33.8 MPa) of 3 wt.% of intact UHMWPE powder impregnated PMMA bone cement. Also, it was found that 3 wt.% of the surface-modified UHMWPE powder with the ratio of 40 (mL) to 0.5 (g) of MMA to PMMA impregnated PMMA bone cement revealed the maximum tensile strength. The curing temperatures of the composite PMMA bone cements decreased from 103oC to 88~95oC. From the above results, we confirmed that the surface-modified UHMWPE powder can use as reinforcing agent to improve the mechanical and thermal properties of conventional PMMA bone cement.