In recent years, bio-based flame retardants have gained significant attention as sustainable alternatives, achieving important breakthroughs in flame retardancy and becoming a key focus for future development. Derived from biomass, chitosan (CS) has been widely used in the field of advanced functional materials. However, in the field of flame retardancy, chitosan alone shows limited effectiveness, leading researchers to explore its reactive functional groups for creating multifunctional flame retardant chitosan composites (FRCC). This review examines FRCC modifications, focusing on how physical and chemical techniques enhance flame retardancy based on combustion mechanisms. Particular emphasis is placed on the impact of embedding flame-retardant elements. Additionally, this paper outlines FRCC performance characteristics, addressing operational requirements in varied environments, and discusses key challenges. This study offers researchers a comprehensive overview of FRCC, serving as a valuable resource for ongoing research and development.