Abstract: Taking wild Leiocassis longirostris from Dongting Lake and original breeding farm as samples and with 20 random primers, we conducted a RAPD analysis of genetic diversity of 10 wild individuals, finding 103 bands whose fragment size are 0.2~3.0 kb, and that each primer generates 2~9 bands with a polymorphic loci proportion of 41.75%.Genetic similarity coefficient and genetic distance within 2 populations are as follows: genetic similarity index(S) of Dongting Lake individuals varies from 0.879 5 to 0.983 3 and that of original breeding farm ones varies from 0.879 4 to 0.989 2;genetic distance(D) varies from 0.016 7 to 0.120 5 and that of original breeding farm ones varies from 0.031 9 to 0.110 8;the genetic similarity coefficient of 2 populations is 0.798 3~0.999 4 and the genetic distance is 0.016 7~0.301 7;Nei genetic diversity index is 0.326 9.The results indicate that L.longirostris has relatively high genetic diversity within populations.