Pyrolysis is a promising technology that can efficiently convert biomass into gas, liquid, and solid fuels. Elucidating the biomass pyrolysis reaction mechanism is essential for the effective biomass utilization. However, the biomass components and structure are very complex, which complicates the investigation of biomass pyrolysis using traditional approaches. Two-dimensional perturbation correlation infrared spectroscopy (2D-PCIS) represents a new analytical method for visualizing the raw Fourier transform infrared spectroscopy data. When volatile compound release properties are studied, the biomass pyrolysis mechanism can be determined. In this paper, the theoretical concept, developments, and applications of 2D-PCIS are described in detail with the emphasis on probing biomass pyrolysis reactions via the analysis of the functional group evolution and bond breakage processes.