From Oct. 1997-June 1999, the paralytic shellfish poisonin (PSP) toxicity levels of scallop Chlamys nobilis and blue mussel Perna viridis, which were collected monthly from four shellfish growing zones in Daya Bay and Dapeng Bay, were determined with the AOAC bioassay method. The results showed PSP was accumulated to a difference levels in the two species and four zones. High toxins levels have been detected in scallop samples from Dongshan station in Daya Bay, from 1263000 to 342000Mu/100g tissue for ingest gland , and from 13400 to 5300Mu/100g tissue for whole tissue excluded ingest gland, and the levels of whole tissue were from 117 to 29.5 Mu/100g tissues during January to May 1999, the toxin levels of whole samples extremely exceeded the public health safety threshold ,but the levels of blue mussel samples from the same station were much less than scallop ,from 567000 to 3100 Mu/100g tissue and from 14200 Mu/100g tissue to undetected for ingest gland and whole tissue excluded former respectively, the levels of whole tissue were from 72800 Mu/100g to undetectable and only one sample`s level was beyond the threshold in January. The levels gradually decreased monthly since winter-spring season . In Aotao , another samples station in Daya Bay, the levels of two shellfish species were lower than the threshold and undetected for most mussel samples . The toxins reached maximum levels at the station during May 1998. Less toxin levels were also detected in the shellfish cultured in Dapeng Bay, however toxins have persisted at lower , still exceeding the threshold , in some scallop ingest gland samples, Relationship among the toxin levels and shellfish species , oceanography , seasonal change was discussed.