Abstract: Horizontal starch gel electrophoresis was used to investigate the genetic structure of sea bass populations. 146 individuals coll ected from coastal waters of China and 40 individuals from Tokyo Bay were examin ed. The proportions of polymorphic loci of sea bass populations varied from 0.26 67 to 0.5333. The values of observed and expected heterozygosity were from 0.021 1 to 0.0515 and from 0.0398 to 0.0797 respectively. There was a nearly complete replacement of alleles at LDH*, GPI-1*, GPI-2* between C hinese and J apanese sea bass. The Nei's genetic distance among Chinese populations varied fr om 0.0004 to 0.0011 with an average of 0.0008. The Nei’s genetic distance betwee n the Chinese populations and Japanese population varied from 0.1870 to 0.1954 w ith an average of 0.19 26. Isozyme analysis indicated that the genetic variation among Chinese populati ons was small, but that between Chinese and Japanese sea bass was much larger th an that among Chinese populations.