Seaweed flora was a sum of all the seaweed populations within definite time and space, with stable temperature, species composition and boundaries. There were two main types of seaweeds which were attached seaweeds and floating seaweeds. In flora study only the attached seaweeds were included, while there was no clear definition of floating seaweeds. Recent years the blooms of floating seaweeds had been a periodical phenomenon within some area in the world, which made it necessary to analyze the relationship between floating seaweed and seaweed flora. With the support from the molecular technology, it was available to carry out tracing and comparative research between attached and floating seaweeds. This paper discussed the relationship between floating seaweeds and seaweed flora. The two main results were: it was still hard to definite floating seaweed as a flora unit; meanwhile, floating seaweed could be a potential connection among different floras.