Method for chromosome prepration of bone marrow cells and short term cultured lymphocytes from Guinea Pig was slightly improved, in order to prepare good chromosomal samples.The analyses of 218 mitotic plates showed that the diploid chromosome number was 64.20 mitosis were used for measurement of each chromosome, other 20 metaphase cells were used for G-banding, while the banding patterns of each chromosome were also analysed and idiogramed. Consequently polymorphism of No.23 chromosome in mitosis were analysed. The results were briefly discussed.