The high species richness and complex community structure of tropical forests pose great challenges to ecologists interested in the function and structure of tropical forests. Plant functional groups (PFGs) are defined as groups of species that either exhibit similar responses to environmental perturbations or have similar effects on major ecosystem processes. PFGs analysis is an effective approach to reduce the complexity of plant communities and to reveal general patterns and processes in tropical forests. In this paper, the concept of PFGs is briefly introduced, the approaches and procedures of aggregation for PFGs are described, and the spatiotemporal dynamics of PFGs in tropical forests are reviewed. PFGs are identified by the functional traits of plants in forest ecosystems. Important functional traits of plants in tropical forests include growth form, potential maximum height, wood density, seed size and dispersal syndrome, leaf size and habits (evergreen or deciduous), and buttress size etc. There are three approaches in aggregating plants into PFGs: intuitive, deductive, and quantitative. Five steps are needed to complete the aggregation process. PFGs replace each other in different successional stages and their relative proportions in the communities change significantly with the process of succession in tropical forest. The assemblages of the PFGs are usually confined by the landscape configuration and environmental heterogeneity. Dynamics of the PFGs are greatly influenced by disturbance regimes and global climate change. In tropical forests, the models based on PFGs have been developed to simulate community dynamics and to predict the potential distribution of vegetations. More detailed studies on PFGs dynamics in tropical forests are needed in the future, in aspects of effective aggregation of PFGs, solid database construction for major functional traits, improvement of modeling based on PFGs, and PFGs-based planning at the landscape level. The PFGs approaches in tropical forests may be extended to other complex forests (e.g. subtropical evergreen-leaved forests).