Abstract: The mechanisms of fish sex determination and differentiation are complex. The current study investigated the morphology and the expression of genes related to sex determination differentiation during development of Yellow River carp. Tissue sections of gonad of Yellow River carp indicated that the time of gonad derived from undifferentiated to stage Ⅱ of testis or ovary were from 40 to 80 dpf (days post-fertilization). The results showed that sex determination related genes (amh, ar, cyp19a, cyp19b, dax1, dmrt1, er, foxl2, nobox, sox9a, sox9b and zp2) highly expressed at 50d, especially at 45-50 dpf. The expression of ar, amh, dax1, dmrt1, sox9a, sox9b increased at 80 dpf in males, which were significantly higher than those in females, suggesting that these genes might mediate male sexual differentiation. The expression of cyp19a, cyp19b, foxl2, nobox, zp2 increased at 80d in females, which were higher than those in males, suggesting that they might regulate female sex differentiation.