Plant communities in cities have obvious beautification and improvement effects on the environment, and at the same time are important places and open spaces for biodiversity conservation. With the acceleration of urbanization, the research and development of urban plant communities has become a trend of urban ecological construction, and making full use of trees is also an important guiding ideology in current urban greening in my country. Therefore, this article conducts a comparative analysis and research on the species diversity of different types of plant communities in the urban area Karachi. In Karachi, which is in the province of Sindh, Pakistan, roadside trees along various road types (e.g., wide, medium and narrow roads) have been studied. Field study has been conducted on different paths of the Karachi city to understand the diversity pattern of the species. A total of 150 plots, divided into 3 categories of roads which were surveyed. The highest quantity of tree biomass per unit area was found on wide roads, followed by medium roads. On narrow roads, the least biomass was detected. A single species or a limited number of species dominated the diversity of species. Conocarpus erectus was the most dominant non-native species along all types of roads, followed by the species Guaiacum officinale. A total of 76 species (32 non-native and 44 native) that were selectively spread along the roadsides of the city were studied. There was a significant difference in phylogenetic diversity (PD), phylogenetic mean pairwise distance (MPD) and phylogenetic mean nearest taxon distance (MNTD) between different types of roads. Our study identified patterns of diversity in roadside trees in Karachi.