Preparation process of C stripping foil used for the beam injection to Heavy Ion Research Facility at Lanzhou-Cooler Storage Ring was studied.The prepared C stripping foil was attached to a U-like shape frame with a double layer structure to increase the strength of stripping foil.The prepared C foil had an effective area of 10 cm~2 and the average thickness of 150 μg/cm~2.The foil has a relatively long lifetime,and can be used in the ultra-high vacuum environments.The result from X-ray diffraction shows that the carbon in the stripping foil occurs as amorphous graphite.