This book is the fifth volume of the “Marine Algal Flora of China-Rhodophyta.” The series has seven volumes covering about 20 orders, 45 families, 173 genera, and 560 species including over 150 species firstly described from China, indicating significant importance to the knowledge of North-Western Pacific marine algal flora. The fifth volume Ahnfeltiales, Gigartinales, Sebdeniales, Nemastomatales, Plocamiales, Gracilariales, and Rhodymeniales. It provides first-hand literatures necessary to phycologists who aimed to study algal taxonomy and diversity, especially in the North Western Pacific region. Almost all species involved are illustrated in detail on morphology, inner structure, habitats, and geographical distribution, based upon herbarium specimens collected along the China coast, and a lot of elaborate pictures are attached inside. This flora will gain our understanding of current Chinese marine red algae, but much research is still necessary to reflect the whole picture of the red algal diversity along the China coast.