The development of vegetative and reproductive structures and life history of Laurencia sp. 1 (Ceramiales, Rhodophyta) had been investigated. The detailed observations of the developmental morphology and life history were undertaken based on field-collected and cultured plants. The materials used in this study show the tetrasporangia originate from a pericentral cell near the growing apex. The sporangia show a parallel arrangement along the axis of the branch and adaxially from the pericentral cell. Mature tetraspores developed into a reddish brown colour upright shoot with colorless rhizoidal filaments. The gametophytic plants are dioecious. Spermatangia or fertile trichoblasts originate from an axial cell near the growing apex and consist of repeatedly dichotomously branched. The spermatangial branches cultured with cystocarpic branches, and then ripe cystocarps formed. The mature cystocarp form a domoid-shaped pericarp with an ostiole, and release carpospores. These carpospores germinated and grew into erect shoot with colorless rhizoidal filaments.