The discrimination between CuCr25 and CuCr50 alloys for the cathode spot craters with peak currents of 10 A and 80 A has been studied in this paper. The microstructure analysis showed that the CuCr alloys has an important effect on the discrimination, in which the size of Cr phase plays an main role in effecting the moving direction and distribution of cathode spot craters. It can well be explained why the chopping current of CuCr25 is less than CuCr50 by the direct measurements of chopping current and arc lifetime by oscillograph. All above useful conclusions will provide powerful supports on decreasing chopping current by minimizing the size of Cr phase for CuCr alloys.