Handomly amplified polymorphic DNA (RAPD) technique was applied to assess the genetic variations and phylogenetic relationshipe in 4 species of Porphyra. The samples were collected from the coast of Canada, Vietnam, Zhoushan, Fuian and Oingdao in China. Amplifications with 20 primers were carried out under predetermined optimal reaction conditions (samples were first heated at 94℃ for 5 min. and followed by 45 cycles of 1 min at 94℃, 1 min at 36℃, and 2 min at 72℃, then held at 72℃ for 10 min). The amplified products were scored as present (1) or absent (0) for each DNA sample and an index of genetic similarity (F) was calculated by using Nei & Li’s matching cocfficient method (1979). The value of (1 - F) was used to quantify the genetic distanes between species and construct a phylogenetic tree. The relationship indicated by the UPGMA and NJ cluster analysis on the values of the genetic distance is in good overall agreement with classical taxonomy. The obvious differences between natural and cultivated population of P. haitanensi suggest that variation or hybridization with other species occurred during the cultare. Handomly amplified polymorphic DNA (RAPD) technique was applied to assess the genetic variations and phylogenetic relationshipe in 4 species of Porphyra. The samples were collected from the coast of Canada, Vietnam, Zhoushan, Fuian and Oingdao in China. Amplifications with 20 primers were carried Samples were first heated at 94 ° C for 5 min. and followed by 45 cycles of 1 min at 94 ° C for 1 min at 36 ° C and 2 min at 72 ° C then held at 72 ° C for 10 The amplified products were scored as present (1) or absent (0) for each DNA sample and an index of genetic similarity (F) was calculated by using Nei & Li’s matching cocfficient method (1979) - F) was used to quantify the genetic distanes between species and construct a phylogenetic tree. The relationship indicated by the UPGMA and NJ cluster analysis on the values ​​of the genetic distance is in good overall agreement with classical taxonomy. The obvious differences be tween natural and cultivated population of P. haitanensi suggest that variation or hybridization with other species occurred during the cultare.