The oxidation behavior of Silicon Carbide Particles (SiCp) was investigated, and oxidized-SiCp reinforced 5052Al matrix composites with SiC volume fraction beyond 55% were prepared by pressureless infiltration. Moreover, the microstructure and interface morphologies of the composites were examined, and its influence on thermal conductivity of the composites was discussed as well. The results show that the oxidation increment of SiCp and the thickness of SiO2 layer increase with the increasing of pre-oxidation time at 1100 °C; when the oxidized time exceeds 6 h at 1100 °C, the rate of the oxidation increment will decline. After oxidation, the sharp edge is obviously passivated for the SiCp; meanwhile, the distribution of the oxidized SiCp in Al alloy matrix is uniform and almost no holes can be found in the composites. Besides, the reaction and combination at the interface are different with the duration time for the oxidation, short-rod-like Al4C3 can be found on the surface of the particles before oxidation, but octahedron MgAl2O4 appears after the oxidation for 4h, and there is still residual SiO2 after the oxidation for 6 h. In addition, the thermal conductivity and interface heat transfer coefficient of the composites both increase at first and then decrease with the increasing of pre-oxidation time, which is closely related with the actual interface status due to different oxidation degrees