Genetic responses of the edible seaweed Porphyra yezoensis tissue to acid shock have been compared using differential display technique. The tissue was challenged in seawater containing $0.05{\%}$ hydrogen chloride (pH 3.0) for 5 min, then rehabilitated in normal seawater for 10 min, 30 min, 60 min and 4 hrs. Total RNA extracted by the LiCl-guanidium method was reverse transcribed and amplified by PCR with arbitrary primers. The amplified fragment responded by the acid shock was selectively isolated from agarose gel and sequenced with DNA auto sequencer. Sequence (1056 bp) of the cDNA contained at least two genes for ASP7K (MW 7418) and ASP5K (MW 5512) proteins.