The composition of microbial communities on leaf surface is closely related to plant foliar diseases. However, the response in fungal community on plant leaves to the severity of pant diseases are still unknown. In this study, we used high-throughput ITS amplicon sequencing technology to investigate the differences in the composition and diversity of fungal com-munity on plant leaves with different disease severities of powdery mildew disease in Solanaceae crops. We analyzed the changes in the topological properties of molecular ecological networks of fungal community and explored the ecological pro-cesses of community phylogenetic assembly. Diversity analysis showed that as the severity of powdery mildew disease in-creased, the richness and diversity of fungal communities gradually decreased. Network analysis revealed that compared to plants with moderate and severe infection, plants with mild disease symptoms had more nodes and connections in the ecological network, with higher network density, clustering coefficient, and average connectivity. Among the plants with different disease severities, the ecological processes of phylogenetic assembly in fungal communities were dominated by stochastic processes, whereas the fungal communities tended to have phylogenetic dispersion with increasing severity of powdery mildew. In conclu-sion, invasive pathogens alter the existing community structure, disrupt the interactions between fungal communities, and influ-ence the ecological processes of community phylogenetic assembly. These findings provide a deep insight into the association between powdery mildew disease and the fungal community on plant leaves.