Abstract: In order to clarify the chromosome composition of wheat high pairing material CS-Ph^I, genomic in situ hybridization and fluorescence in situ hybridization were used for molecular cytogenetic identification. The powdery mildew resistance gene of wheat high pairing material CS-Ph^I was derived by 23 different powdery mildew strains with different virulence, and the powdery mildew resistance was identified by inoculating with mixed strains at the adult stage. The results showed that the translocation chromosome of CS-Ph^I was a biterminal small fragment translocation between Triticum aestivum chromosome 6B and Aegilops speltoides. The resistance spectrum of CS-Ph^I was similar to Pm4 c or Pm3 b, and it was immune to powdery mildew at the adult plant stage. CS-Ph^I could be used in wheat powdery mildew resistance breeding, but whether it was a new gene needs to be comprehensively analyzed and studied.