Numerical analysis of global heat transfer with coupled thermal radiation and heat conduction is investigated in Czochralski silicon crystal growth furnace with curved diffuse and specular surfaces. The finite element method and the radiation element method are adopted to solve the global heat transfer and the radiative heat exchange, respectively. The emphasis focuses on the discussion of the influence of silicon surface radiative characteristics, i.e., either diffuse or specular, ion the global heat transfer and the crystal growth process. When the specular character of the silicon crystal and melt surfaces is considered, it is found that the temperature of the melt is obviously decreased and the crystal pulling rate is enhanced.