In this paper, the number and karyotype of chromosomes, DNA content, the mean nuclear erythrocyte volume, gonads and gametes, embryo development, the mechanism of the tetraploid formation, and the appearance in tetraploid hybrid stocks of the red crucian carp (♀）× common carp (♂）were described. The tetraploid hybrids with stable genetic characteristics were inherited from F3 to F11 and a large population of tetraploid fish had been formed. The tetraploid hybrids were essentially different from their parents-red crucian carp and common carp in chromosome number, reproduction and appearance. Based on the genetic characteristics, the bisexual fertility and reproductive isolation, the tetraploid stocks had possessed the good base to form a new tetraploid species in the future. The formation of the new tetraploid stocks had great significance both in the evolutionary theory of vertebrate and in the production application.