Abstract: To further study the breeding strategy for Penaeus monodon, we investigated the genetic relationship among 7 full-sib P.monodon families.From 95 pairs, 16 pairs of microsatellite primers were selected, and among 16 microsatellite loci 79 alleles were discovered.Each locus has 2~10 alleles and 4.937 5 on average; effective allele number ranges from 1.757 5 to 5.398 0 and 3.387 8 on average; average observed and expected heterozigosity value is 0.667 9 and 0.669 8, respectively; average polymorphism information content(PIC)is 0.611 0.Global heterozygote deficit across 7 families(F_IT) reaches 0.009 9, inbreeding coefficient(F_IS) is-0.372 5 and genetic differentiation coefficient(F_ST) reaches 0.270 9.According to the genetic distance, we conducted a clustering analysis of the 7 families by UPGMA.The results indicate that F2 and F6 cluster into one group with the minimum genetic distance, while the genetic distance between F2 and F7 is the furthest.Thus, the genetic differentiation among 7 families is relatively higher, with less gene flow and less inbreeding.F7 should be given prior consideration for hybrid breeding.