Abstract The temperature rise and weight loss characteristics of wheat straw and their mixture under microwave irradiation have been investigated in the laboratory with a fixed bed microwave reactor. The influences of both the microwave power and the additives on the temperature rise and weight loss characteristics of wheat straw are the focuses of this work, which aims to explore a new theoretical foundation for advanced pyrolysis methods. The temperature rise curves show that pure wheat straw had a weak capability to absorb microwave energy, while the mixture of wheat straw and pyrolytic residue had a very strong absorption capability. The ability to absorb microwave energy of the mixture increased with increasing amount of pyrolytic residue. These results are in good agreement with the results of the weight loss curves. Thus, it is feasible to pyrolyze wheat straw in microwave fields by addition of small amounts of pyrolytic residue.