Abstract: Random amplified polymorphic DNA (RAPD) technology was employed to investigate the genetic diversity and structure of 6 Scylla paramamosain populations in Guangxi and its neighboring sea areas. We amplified a total of 99 individuals by using 8 random primers with 10 bp in length, and analyzed 44 valid loci, among which 31 loci are disclosed as polymorphism. The percentage of polymorphic locus (PPL) at species level is 70.45%. According to POPGENE analysis, the PPL in the 6 populations ranges from 29.55% to 54.55% with an average of 36.97%. The abundance of genetic diversity is QZWDJZZWZKQHLSW. Variance within populations is higher than that among populations, and genetic differentiation among populations reaches higher level. An analysis of molecular variance (AMOVA) shows that variance within populations accounts for 87.03%, andthat among populations accounts for 12.97%. However, genetic differentiation among populations only reaches medium level. Mantel test shows that no significant correlation between genetic and geographic distance is detected in the 6 S.paramamosain populations. Cluster analysis indicates that the distribution of these populations displays no apparent geographic pattern.