In order to identify feature of species-specific molecular of edible seaweed,we used the Plant Genomic DNA Kit to collect the four kinds of common edible marine algae( Ulva lactuca L,Gracilaria verrucosa,Laminaria japonica and Spirulina) samples DNA and then verify the specificity of different primers by PCR technology. At last, the multiplex PCR technology was used to verify the primers sensitivity. The results showed that four kinds of common edible marine algae( Ulva lactuca L,Gracilaria verrucosa,Laminaria japonica and Spirulina) all obtained the corresponding single band with different sizes,which demonstrated the specificity of the primers and without nonspecific amplification. The minimum detection limit of the duplex-PCR method for Ulva lactuca L and Gracilaria verrucosat was 362pg and 100pg,respectively.