The pyrolysis and combustion characteristics of three biomasses and five model components in a newly designed macro thermogravimetric analyzer (macro-TGA) were compared. The comparison of model component combustion in the thermogravimetric analyzer (TGA) and macro-TGA was conducted too. The results showed that the behavior of model component combustion was significantly different between the TGA and macro-TGA. In the macro-TGA, the maximum peaks of derivative thermogravimetric (DTG) curves derived from model component combustion occurred at similar temperatures compared to their pyrolysis, while for biomasses, the main peaks appeared earlier in combustion. The biomasses could be simulated by main components well in both pyrolysis and combustion in the macro-TGA, while the five model component (hemicellulose, cellulose, lignin, starch, and pectin) simulation fitted the experimental result better than the three biomasses (hemicellulose, cellulose, and lignin). However, the fractions differed from each other significantly in different atmosphere simulations.