In 1999 and 2000 , gynogenesis was carried out based on 32year old ( F5) and 22year old ( F6) fish respectively, in order to maintain the response of genetic improved blunt snout bream ( Megalobrama amblycephala) which was named strain Pujiang 1 (selected for 15 years ) , and establish pure lines for further study. Gynogenetic fry were produced by cold2shocking eggs , activated with UV2irradiated common carp sperm (1∶3 diluted , two Philips 30W germicidal tubes , 253. 7nm , 10cm distance between lamp and sperm surface) , inhibiting the second polar body extrusion. The optimal treatment conditions including cold2shock temperature , treat time after fertilization and duration time were investigated and selected to fit for 22year old eggs and 32year old eggs. The optimal treat time after fertilization was similar 3min in 22year and 32year old eggs. But the optimal cold2shock temperature and duration time had some differences (0 -2 ℃, 30min for 32year eggs and 42 6 ℃, 20min for 22year eggs) . Three gynogenetic groups were established and more than 1000 normal gynogenetic fry were produced by 22year experiment. Using RAPD methods , heredity differences (genetic variations ) of gynogenetic fry (G1) and non2gynogenetic fry (F6) were compared and analyzed. The 1100bp band amplified by primer S8 was only found in F6 group , the 860bp band amplified by primer S18 was only found in gynogenetic fry ( G1) group . The two bands could be used as molecular markers of these two groups . The genetic distance among gynogenetic fry G1 was much less and only 54 % of F6 group.