This article elaborates in detail the research progress in improving the interfacial interaction between fibers and polymers. Fiber-reinforced polymer composites have broad application prospects in many fields, but the poor interfacial compatibility between fibers and polymer matrices (such as epoxy resin, polyetheretherketone, polyethylene terephthalate, etc.) affects their applications. Modifying fibers through methods such as plasma treatment, silane treatment, and chemical grafting can improve the interfacial compatibility and enhance the performance of composite materials. The article introduces the methods for improving the interfacial compatibility of polymer composites reinforced with carbon fibers, ramie fibers, and basalt fibers, etc. For example, bamboo fibers can improve the interfacial compatibility through plasma treatment and encapsulation processes; the mechanical properties of ramie fibers are enhanced after modification with silane coupling agents, but the influence of the modification on the high-temperature molding process needs further study; basalt fibers can improve their interfacial compatibility with polymers through dual modification and other methods. In addition, the related research on carbon fiber and aramid fiber-reinforced polymer composites is also discussed. In the future, it is necessary to achieve the multifunctionalization of composite materials and adopt new production technologies and modification methods to meet the application requirements in different fields.