Abstract: The root tips of P. macgregorii seeds was used as the research material to investigate the effects of different pretreatment reagents, pretreatment time and dissociation methods on the chromosome preparation of P. macgregorii root tips. A set of chromosome preparation technique of P. macgregorii was obtained and used as the basis for karyotype analysis to reveal its karyotype characteristics, providing a foundation for the conservation and genetic research of P. macgregorii. The results showed that pretreatment with 0.003 mol/L 8-hydroxyquinoline in the dark for 6 h, fixation with Carnoy's fixative for 10 h, dissociation with 1 mol/L HCl in a constant temperature water bath at 60 ℃ for 12 min, and staining with 20% carbol fuchsin could obtain high-quality chromosome squash of P. macgregorii with good dispersion and clear morphology. The chromosome number of P. macgregorii was 2n=24, and the karyotype formula was 2n=24=20m+4Sm, with an asymmetry coefficient of 55.77%. The karyotype was classified as type 1B.