) is an important cultured marine fish species in northern China. Females grow three to four times faster than males. The low growth rate of males leads to an overall reduction in production, thus reducing their value. Given this, the development of all-triploid stocks would be a significant benefit to the commercial aquaculture of half-smooth tongue sole. We developed a method for in this species. The optimal initiation time for pressure shock of fertilized eggs was 21.5 min after fertilization at 23C. The optimal pressure and treatment duration were 40 MPa and 4.5 min, yielding a tetraploid rate in fry of 68.3%. We analyzed the ptetraploid DNA relative content was two times that of chromosomes in triploid fry, whereas normal diploid fry have 42 chromosomes. Our method provides