The rapid expansion of markets for new energy power generation systems, electric vehicles, and drones has driven a significant surge in the demand for lithium-ion batteries (LIBs). However, traditional liquid-state LIBs face critical challenges, including a low energy density, significant safety risks, and a limited operational lifespan. Solid-state lithium batteries (SSLBs) have emerged as a promising solution, offering a higher energy density and improved safety, with their industrialization reliant on advancements in solid-state electrolytes (SSEs). Among these, polymer-based SSEs stand out for their lightweight, cost-effective, flexible, and easily processed nature, making them ideal for large-scale production. Notably, polyimide (PI) has gained significant attention as a leading candidate for polymer-based SSEs because of its excellent mechanical properties, thermal stability, flexibility, and flame retardancy. This review systematically examines the application of PI-based solid electrolytes (PISEs) for SSLBs, starting with their structural designs, material types, mechanisms, and key properties. It then delves into preparations, modification strategies, and advanced architectures while presenting application scenarios and performance metrics. Finally, this review highlights potential future directions for the development and optimization of PISEs for SSLBs. It will lay a solid theoretical foundation for the extensive research and application of PI in the field of SSEs and greatly promote the development of high-performance and high-security SSLBs.