Tropical forest ecosystems are one of the richest terrestrial ecosystems which support a variety of life forms and maintain huge global biodiversity. The phytosociology is one of the important aspects for analyzing the structure, composition and phytodiversity for thoroughly understanding the vegetation dynamics. Both structure and diversity of vegetation have strong functional role in controlling ecosystem processes like biomass production, cycling of water and nutrients. Phytosociological studies revealed that the southern hill top tropical evergreen forest has high species richness and diversity. The study of plant community implies knowledge of structure and composition of the component species. The combined influence of plant height, basal area, density and number of species on ‘complexity index’ is the evaluation of vegetation physiognomy. The present study analyses the compositional attributes of Neyyar wildlife sanctuary. The phytodiversity is one of the important aspects for analyzing the structure, composition and for thoroughly understanding the vegetation dynamics. Both structure and diversity of vegetation have strong functional role in controlling ecosystem processes like biomass production, cycling of water and nutrients.