The commonly used CCD in Raman spectroscopy is sensitive to temperature, and cooling can effectively reduce its dark current noise. A cooling system is designed, and the finite element analysis software ANSYS is used to simulate the heat conduction of the heat sink and the heat exchange of gas flow in the vacuum chamber. The temperature change with the cooling time is measured at different vacuum degrees and with different buffer gas including Ar, Ne, N2 and air. The experimental results show that better cooling effect can be realized when N2 is used as buffer gas, and higher vacuum degree does not guarantee better cooling effect, which is consistent with the thermal simulation result. The measured dark current noise of CCD at different temperatures shows that CCD temperature has strong impact on its dark current noise, cooling can reduce the noise effectively, and the noise varies with temperature exponentially.