Abstract: The paper reported that the chromosome number of S. japonicum consisted of eight pairs (2n = 16), which were divided into three size groups: A, B, and C. In Group A, No.1 was subtelocentric (st) and No.2 was submetacentric(sm). In Group B, No.3-5 were subtelocentrics (st). In Group C, 6 and 7 were subtelocentrics (st) and 8, the smallest, was metacentric (m). The submetacentric chromosomes were sex chromosomes, the females were heterogametic (ZVV) and the males were homogametic (ZZ). The auto-somes with more subtelocentrics in S. japonicum were different from the karyotype of S. mansoni.