Abstract: A profound study on the characteristics of pyrolysis and combustion of biomass and the generation and transfer of alkali metals can provide theoretical basis for the clean and efficient utilization of biomass. Due to the low measurement accuracy and time lag, traditional measurement methods have insufficient understanding of the biomass thermal reaction process. Laser induced fluorescence (LIF) technology has the advantages of non-disturbance, real-time in-situ measurement, strong component selectivity, good sensitivity, and high spatial and temporal resolution, which has been used in more and more studies on the biomass thermal reaction processes. This paper mainly reviews the application of LIF technologies in the research on the characteristics of biomass pyrolysis, combustion, and alkali metal release in recent years, analyzes the release and evolution behavior and formation mechanism of volatile matter during biomass pyrolysis under different reaction conditions, and expounds the flame structure information and alkali metal release, migration, and transformation characteristics during biomass combustion. Finally, some shortcomings in the current research and the future research directions are put forward.