Abstract: Cytochalasin B (CB) was used for inhibiting the first cleavage of zygotes to induce tetraploid in Macrobrachium nippo-nense. At 18-19℃ and 22-23℃ water temperature, two tetraploid induction trials designed by L9(34) were carried out using CB treatment at different beginning time after fertilization (5 hours, 6 hours, 7 hours, 8 hours, 9 hours), different concentration of CB (110mg/L, 115mg/L,210mg/L), and different treatment duration time of the eggs (1.0 min, 1.5 min, 2.0 min)1 The re-sults indicated that the highest induction rate at 18-19℃and 22-23℃ were 56.1% and 54.3% respectively. The optimum condition of inducement tetraploid at 18-19℃ was that treatment beginning timewas 7-8 hours after fertilization, CB concen-tration was 1.5mg/L, and treatment duration was 20min. The optimum condition of inducement tetraploid at 22-23 e was that treatment beginning timewas 6 hours after fertilization, CB concentration was 115mg/ L, and treatment duration was 15-20min. The lowest induction rate at 18-19℃and 22-23℃were 28.5% and 20.1% respectively at the experimental condition of 1.0mg/ L CB concentration, beginning treatment at 5-7 hours after fertilization, and 10 min treatment duration time1 Beginning time of CBtreated and the concentration of CB significantly affected the induction rate of tetraploid (P 0.05). Significantly different hatching rate were observed between three different CB concentration (P< 0.05). As the increase of CB concentration, the damage of embryo was increased, the hatching rate was reduced (P< 0.05). Combining to induction rate of tetraploid, the survival rate of embryo and hatching rate, the treatment condition of 1.5mg/L of CB concentration and 20min treatment duration were recommended1