Indoor mildew prevention is a global building safety issue. Zinc oxide (ZnO) is used in paints as an inhibitor and for mildew control. However, research on the impact of antifungal paint on wall mildew’s fungal community is limited. The aim is to investigate the fungal diversity of mildew on wall surfaces and their selection affect by ZnO. In this study, patches of mildew naturally formed slowly on a wall which was treated with six concentrations of ZnO paint five years ago. Mildew infestation levels showed a negative correlation with ZnO concentrations. Increasing of ZnO concentration decreased mildew infestations effectively. Fungal hyphae colonized the wall surface and penetrated through the layers of paint and plaster through SEM observation. Studies of indoor microbiome rely on cultured-based methods, microscopic, biochemical, and molecular identification. Sequence-based approaches offer more efficient and perform quantitative analysis to identify fungal communities. We employed high-throughput sequencing to analyze the fungal community of mildew. Twelve fungal genera, with Acremonium, Cladosporium, Devriesia and Neodevriesia being dominant, which were found in all treatments with varying dominance levels. The growth of Circumfusicillium and Cyphellophora was inhibited by high concentrations of ZnO, while Septofusidium and Simplicillium were tolerated. We are isolating wall mildew fungi to determine their ZnO and drought resistance or tolerance. We are interested in which fungi being selected and how they tolerate the stress that enable them to corrosion wall and form mildew.