In the present study, a chromosomal observation on the heteromorphic marine red alga Porphyra haitanensis Chang et Zheng was conducted, mainly to ascertainwhere the meiosis occurs in the life history of the dioecious Porphyra. The living materials of differen t life phases in P. haitanensis were fixed in Carnnoy’s fixative fluid, and stored at the light conditions to leach phycobilin pigments. The samples were then stained with Wittmann’s acetoiron haematoxylinchloral hydrate and examined under a photomicroscope (Olympus BH) with oil immersion lens. Chromosome counts indicated that spermatia, vegetative cells gametophytic blade and conchospore germlings are haploid (n=5); whereas carpospores, conchocelis, conchosporangial cells and conchospores are diploid (2n=10). The cell divisions that occurred in spermatia, carpospores and conchocelis are mitosis. Leptonema, diplonema, diakinesis, metaphase and anaphase of the meiosis and the change in ploidy at the twocelled stage were observed in conchospore germlings. Characteristics of the first division of conchospore and the change in ploidy at the two celled stage indicate that meiosis occurs during the germination division of conchospore in Porphyra haitanensis.