The influence of mineral matter on pyrolysis of biomass (including pure biomass components, synthesized biomass, and natural biomass) was investigated using a thermogravimetric analyzer (TGA). First, the mineral matter, KCl, K 2 CO 3 , Na 2 CO 3 , CaMg(CO 3 ) 2 , Fe 2 O 3 , and Al 2 O 3 , was mixed respectively with the three main biomass components (hemicellulose, cellulose, and lignin) at a weight ratio (C/W) of 0.1 and its pyrolysis characteristics were investigated. Most of these mineral additives, except for K 2 CO 3 , demonstrated negligible influence. Adding K 2 CO 3 inhibited the pyrolysis of hemicellulose by lowering its mass loss rate by 0.3 wt%/°C, while it enhanced the pyrolysis of cellulose by shifting the pyrolysis to a lower temperature. With increased K 2 CO 3 added, the weight loss of cellulose in the lower temperature zone (200–315 °C) increased greatly and the activation energies of hemicellulose and cellulose pyrolysis decreased notably from 204 to 42 kJ/mol. Second, studies on the synthetic biomass of hemicellulose, cellulose, lignin, and K 2 CO 3 (as a representative of minerals) indicated that peaks of cellulose and hemicellulose pyrolysis became overlapped with addition of K 2 CO 3 (at C/W=0.05–0.1), due to the catalytic effect of K 2 CO 3 lowering cellulose pyrolysis to a lower temperature. Finally, a local representative biomass—palm oil waste (in the forms of original material and material pretreated through water washing or K 2 CO 3 addition)—was studied. Water washing shifted pyrolysis of palm oil waste to a higher temperature by 20 °C, while K 2 CO 3 addition lowered the peak temperature of pyrolysis by ∼50°C. It was therefore concluded that the obvious catalytic effect of adding K 2 CO 3 might be attributed to certain fundamental changes in terms of chemical structure of hemicellulose or decomposition steps of cellulose in the course of pyrolysis.