The chromosome numbers and the karyotypes of seven species in Unionidae are reported, using air drying in gonad. In seven species, the chromosome number of 38(2n) was counted. The mitotic chormosomes of A. arcaeformis flavotincta, A. woodiana and L. gottschei hd 7 pairs of metacentric and 12 pairs of submetacenrtic chromosomes, U. douglasiae had 6 pairs of metacentrics, 13 pairs of submetacentrics, U. douglasiae sinuolatus had 4 metacentric pairs and 15 submetacentric pairs, L. acrorhyncha had 5 metacentric pairs and 14 submetaacentric pairs, and S. triangularis had 5 mdtacenrtric pairs, 13 submetacentric pairs and 1 pair of subtelocentric chromosomes. The size of chromosomes of A. woodiana was the longest in length and L. gottschei was the shortest. The sexual difference of chromosomes was not observed.