Abstract: Seed endophytic fungi are a type of fungi that spread through vertical transmission and have a mutualistic symbiotic relationship with host plants. They can be classified into three types based on their colonization sites and output characteristics. Currently, research on endophytic fungi in seeds mainly focuses on the Poaceae and Fabaceae plants. Seed endophytic fungi exhibit species diversity and community diversity, which not only manifest in the interspecies of plants, but also in different tissues of plants. Seed endophytic fungi have diverse functions, which can affect soil properties, improve seed germination, assist in seedling establishment, promote plant growth, enhance plant stress resistance, and influence plant community structure. Detecting and identifying species is the foundation of research on endophytic fungi in seeds, and figure out the structure of seeds and the colonization sites of fungi are the preliminary and basic work for detecting endophytic fungi in seeds. Currently, the research on seed endophytic fungi mainly includes identifying its species and their diversity, functions and their diversity, roles in the host's life history, and development and utilization. In terms of research methods, scanning electron microscopy can be used to observe the structure, morphology, and colonization location of fungi; whole-genome sequencing (WGS) technology can obtain microbial genome data and reveal the molecular mechanisms of interaction between seed endophytic fungi and plants. In terms of research content, species diversity, community diversity, ecosystem diversity, and development and utilization of seed endophytic fungi have become hot issues. Looking to the future, research on seed endophytic fungi is a field with great development prospects.