To better understand biomass pyrolysis, the different roles of the three components (hemicellulose, cellulose, and lignin) in pyrolysis are investigated in depth using a thermogravimetric analyzer (TGA). The pyrolysis characteristics of the three components are first analyzed, and the process of biomass pyrolysis is divided into four ranges according to the temperatures specified by individual components. Second, synthesized biomass samples containing two or three of the biomass components are developed on the basis of a simplex-lattice approach. The pyrolysis of the synthesized samples indicates negligible interaction among the three components and a linear relationship occurring between the weight loss and proportion of hemicellulose (or cellulose) and residues at the specified temperature ranges. Finally, two sets of multiple linear-regression equations are established for predicting the component proportions in a biomass and the weight loss of a biomass during pyrolysis in TGA, respectively. The results of the calculations for the synthesized samples are consistent with the experimental measurements. Furthermore, to validate the computation approach, TGA experimental analysis of the three components of palm oil wastes, a local representative biomass sample, is conducted.