Triploid of Pacific oyster Crassostrea gigas Thunberg was induced by blocking pb2 w ith cytochalasin B ( CB) and 6- dimethylaminopurine ( 6- DMAP) and the triploid seed had been farmed with suspended longline in the sea. The egg was fertilized at 25 e and treated with 0. 5mg#L - 1 CB begun at 20- 30min pos-t fertilization lasted 18- 22min. Incubated density of zygote when treatment was about 4. 0- 4. 5 @ 107ind#L- 1. Triploid yield was 65. 2%- 70. 1% and velar larvae gain was 12. 3% - 14. 5%, and the eff iciency of triploid induction( ETI) was 0. 09. The concentration of 6- DMAP used to the induction of triploid was 400- 420 Lmol#L- 1 and the zygote density for treatment was 3. 0- 3. 5 @ 10 7 ind#L - 1 . Triploid yield was 58. 7% - 65. 4%, velar larvae gain was 52. 1% - 55. 4% , and ETI was 0. 32. The surrounding temperature when fert ilization, initial and lasting time for the triploid treatment were the same as those in CB. Spat harvest on the scallop shell which was as the collector was similar to both those in CB and 6- DMAP. The traits of the triploids induced by CB and 6- DMAP farmed for 14 months showed no significant difference in growth, meat harvest and condition index. Comprehensive comparison between the two methods showed that 6- DMAP was more applicable in triploid production than CB.