Induction of adding chemical compounds on the sett lement metamorphosis of Saccostreea cucullata larvae was assayed. The metamorphosis of larval Saccostreea cucullata can be induced by epinephrine ( EPI) , Norepinephrine ( NE) , and L - DOPA. During a 48h exposure, optimum concentrat ions of three compounds were 10- 5mol..L- 1, 5 .. 10- 5mol..L- 1 and 10- 5mol..L- 1 corresponding to maximum metamorphosis rates of 67. 4% , 52. 2% and 43. 0% respectively. Most metamorphosis occurred in the period of 12- 24 h. Over 85% of larvae metamorphosed without attachment . NE can be deprived of its inductive activity when oxidized in seawater to be orange/ brown substances. Exposure time has signif icant inf luence on metamorphosis induction. NE produced the highest metamorphosis rate w ithin 2h, and effect ive concentration was inversely proportional to time in the range of 5 .. 10 - 6 mol..L - 1 ~ 5 .. 10 - 4 mol..L - 1 during this short period. L- DOPA brought about the maximum rate within 30min in the range of 5 .. 10 - 6 mol..L - 1 ~ 10 - 5 mol..L - 1 . A 5 min exposure to 10 - 5 mol.. L - 1 ~ 10 - 4 mol..L - 1 L- DOPA may enhance metamorphosis through attachment. Comparison of induct ive effect between artif icial inducers and chemical active substances ( CAS) that CAS is more active. NE- induced postlarvae well survived in low salinity but badly in high salinity.