Abstract: The polyploidy sea cucumber \%Apostichopus japonicus\% (Liao) were induced to get the eggs and sperm by ultraviolet irradiated sea water in order to control the beginning time of the inducement. The polar body I was inhibited 5 and 10 minutes after fertilization by \{0.2\} and 0.4 mg/L cytochalasin (CB). The polar body I and polar body II were inhibited 5, 10, 20, 28,or 35 minutes after fertilization by 10,20,30,or 40 mg/L 6-dimethylaminopurine (6-DMP), repectively. The relationship between occurrence of the polyploidy and the chemicals density, shocking time lasting, and the initial time of shocking were studied. It was found that triploid and tetraploid can be induced by the two chemicals, with 21.3% tetraploid by CB and 25.8% triploid by 6-DMAP. There wae no significant diference in feeding, growth, time lasting of floating and metamorphism between treated groups and the control.