Vertical polyamide gel electrophoresis was used to investigate isozyme polymorphisms among different isolates （including wild and cultivated） of Porphyra katadai, Porphyra oligospermatangia, Porphyra yezoensis, Porphyra haitanensis, and a hybridize species （Porphyra yezoensis x Porphyra haitanensis） sampled from China. Whereafter, the analyses of probable minimum loci numbers, observed alleles sum, genetic diversity, and unweighted pair-group arithmetic average （UPGMA） cluster were carded out. After initial activity and resolution testing of bands of 23 enzymes, 6 of them （MDH, ME, LDH, GDH, IDH and G-6-PDH） were proved to be appropriate for analysis of the full sample set. The probable minimum numbers of loci and alleles analyses showed that the five species of Porphyra had an extraordinary consistent result in ME loci and alleles. However, P. katadai and P. oligospermatangia differed from other three species of Porphyra in LDH and GDH loci and alleles. P. katadai was independent in the analyses of MDH and P. oligosperTnatangia and P. haitanensis differed from other three species in IDH analyses. Moreover, P. yezoensis and P. haitanensis were apart from other three species in G-6-PDH analysis. Taking one with another, P. katadai was relatively separated in the probable minimum numbers of loci and alleles analyses. The results indicated that the genetic variation among the five Porphyra species was limited with a genetic identity of 0.7550. The hybridize species （P. yezoensis x P. haitanensis） seemed to be high homologue with P. oligospermatangia, unexpectedly got relatively lower average genetic identities with both P. yezoensis and P. haitanensis. The 4 strains of P. yezoensis were relatively divergent with an average genetic identity of 0.7428, and P. katadai presented the most differentiated, compared with other species, which consistented with the result summarized in the probable minimum numbers of loci and alleles analyses.
