Polycarbonate (PC)/graphene oxide (GO) composites with 3 phr of GO were prepared by using a twin screw extruder at 240, 260, and 280 ℃ after mixing the solution with chloroform. It was confirmed by DSC and TGA that the glass transition temperature (Tg) of PC/GO composites were not changed and the thermal stability was the best in case of the extrusion temperature at 260 ℃. Thermo mechanical properties of PC/GO composites according to extrusion temperatures were measured by dynamic mechanical analysis (DMA). Storage moduli of PC/GO composites were higher than that of pure PC and there was no detectable changes at varying the extrusion temperature. Based on these results, the extrusion temperature of PC/GO composites was fixed at 260 ℃. The degree of the chemical reaction of PC/GO composites with respect to the GO reduction time was confirmed by the C-H stretching peak at 3000 cm-1 and the degree of the chemical reaction was similar to that of GO when the reduction time was 1 h. A decrease in the complex viscosity as a function of the GO reduction time was detected by dynamic rheometer, which may be originated from the enhancement of GO dispersion by PC-GO reaction. The GO dispersion was confirmed by scanning electron microscope (SEM).