We studied the gonadogenesis, gender differentiation and early stage development of doubled haploid Japanese flounder (Paralichthys olivaceus) by using histological sections. The results indicated that there were some female, male and also undifferentiated individuals in the doubled haploid population, and the ratio was 56%: 38%: 6%. The gender differentiation in female doubled haploid was later than the normal one. At 100 days, the ovarian cavity was still not closed; and at 110 days, there were a large number of transitional cells from oogonium to oocyte on the spawning board, and the stageⅠoocyte was not observed. For the male double haploid, the gender differentiation was basically the same in time with the normal one. With the development of gonad, there were some abnormal oocytes in the ovaries of double haploids, and some ovaries degenerated. There were also some degeneration appeared in the testes of male doubled haploids. At 9-11 months old, the testis of doubled haploid was at stage Ⅲ, while the testis of normal Japanese flounder develop into stage Ⅳ. From 11 months, the testes of some doubled haploid begun to degenerate. At 13-15 months old, there were only spermatogonium in the seminiferous lobules, and the primary spermatocyte disappeared, like the testis in stageⅡ.