Biomass pyrolysis is a promising thermal chemical processing technology to produce renewable and sustainable energy materials. However, the interaction between biomass components (cellulose, hemicellulose and lignin) during pyrolysis process needed further investigation. In this work, an in-situ Reflectance Infrared Fourier Transform Spectroscopy (in-situ DRIFTS) reactor was introduced to investigate the interactions assisted with Thermogravimetric Analysis (TGA). The experiments demonstrate that there exist complicated interactions between the main components of biomass during pyrolysis. The results from TGA/DTG indicate that the interactions between cellulose and xylan introduce higher pyrolysis temperature, while the interactions between cellulose and lignin, xylan and lignin, resulte less weight loss. The increase of compression pressure for the mixture of main components changes the weight loss of the mixture. The results from in-situ DRIFTS show that the decomposition and aromatization of xylan are promoted when the cellulose is added. Cellulose will also hinder the accumulation of the benzene rings of the lignin. The in-situ DRIFTS experiment results also suggest that the contact pressure between the components conduct more residue solid, mainly because the dehydration reaction of the mixture samples was inhibited and the charring process was promoted, especially the reaction between cellulose and lignin. (C) 2018 Elsevier Ltd. All rights reserved.