Changes of paralytic shellfish toxin components and specific toxicity in blue mussel, Mytilus edu/is and oyster, Crassostrea gigas during canning process were investigated by high performance liquid chromatography (HPLC). The $mole\%$ of the frozen shucked blue mussel were in order of $27.5;mole\%$ of gonyautoxin 1, $23.0;mole\%$ of gonyautoxin 8 (C1) and $23.0;mole\%$ of epi-gonyautoxin 8 (C2), while those of the frozen shucked oyster were in order of $29;mole\%$ of C1, $22;mole\%$ of C2, $16.7;mole\%$ of gonyautoxin 2. Both samples had minor amounts of saxitoxin and neosaxitoxin. On the other hand, in case of specific toxicity, the major toxins were consisted of gonyautoxin $1~4$ in both sample. The toxicity of gonyautoxin $1~4$ were 88 and $84\%$ in blue mussel and oyster, respectively. According to the experimental results, C1, C2 and gonyautoxin 4 were very sensitive to heat treatment, while gonyautoxin 2 and saxitoxin were pretty heat resistant than any other toxin components.