At present, studies on the relationship between endogenous phytohormones and growth and development of macroalgae are still lacking. In this study liquid chromatography-mass spectrometry (LC–MS) was used to investigate the temporal and spatial changes of the types and contents of major endogenous plant hormones in Sargassum fusiforme holdfasts during the juvenile's regeneration. The results showed that six endogenous hormones or hormone precursor substances including auxins (Aux/IAA), gibberellins (GAs), isopentenyl adenine (2-iP), 1-aminocyclopropanecarboxylic acid (ACC), salicylic acid (SA) and dihydrojasmonic acid (DHJA) were detected at different temporal change and in different parts of S. fusiforme holdfasts and the regenerated juveniles. The contents of Aux/IAA, 2- iP, ACC, SA and DHJA decreased gradually from non-regenerated (NG) to initial regeneration (IG) of juveniles. From the perspective of spatial distribution, among the leaves (SL), stems (SS) and new holdfast filaments (SR) of the regenerated juvenile, Aux/IAA and GAs contents were the highest in SL and the lowest in SR, while the contents of DHJA and SA were the opposite. The endogenous hormones during the regeneration of juveniles from holdfasts had dynamic pattern of temporal and spatial changes. When compared with other brown algae by the clustering analysis, it was found that the regenerated juveniles had a higher Aux/IAA and SA contents, while the gibberellin (GA3) content varied greatly. This may be the potential cause of regeneration of juveniles from S. fusiforme holdfasts. This study lays the foundation for the study of hormone regulation mechanism during the regeneration of juveniles from S. fusiforme holdfasts and provides a theoretical basis for S. fusiforme holdfasts seedlings. [ABSTRACT FROM AUTHOR]