This review discusses the development and application of sulfide-based composite solid electrolyte films for all-solid-state batteries (ASSBs). Sulfides are favored for their high room-temperature ionic conductivity and low-temperature processing, but large-scale thin film fabrication remains challenging. The introduction of polymers as binders or frameworks has enabled the creation of flexible, thin sulfide-based composite electrolyte films with high ionic conductivity. The review covers the ionic transport mechanism, preparation methods, and properties of these composite electrolytes, analyzing the advantages and disadvantages of each method. It also explores the application of these films in ASSBs and provides a perspective on future research directions. Key findings include the use of tape casting for large-scale production, the importance of selecting appropriate solvents and binders to enhance ionic conductivity, and the need for further research on binder compatibility with lithium metal anodes to improve interface stability and cycling life.This review discusses the development and application of sulfide-based composite solid electrolyte films for all-solid-state batteries (ASSBs). Sulfides are favored for their high room-temperature ionic conductivity and low-temperature processing, but large-scale thin film fabrication remains challenging. The introduction of polymers as binders or frameworks has enabled the creation of flexible, thin sulfide-based composite electrolyte films with high ionic conductivity. The review covers the ionic transport mechanism, preparation methods, and properties of these composite electrolytes, analyzing the advantages and disadvantages of each method. It also explores the application of these films in ASSBs and provides a perspective on future research directions. Key findings include the use of tape casting for large-scale production, the importance of selecting appropriate solvents and binders to enhance ionic conductivity, and the need for further research on binder compatibility with lithium metal anodes to improve interface stability and cycling life.