In this paper, pyrolysis of Indonesian oil sands (IOS) was investigated by two different heating methods to develop a better understanding of the microwave-assisted pyrolysis. Thermogravimetric analysis was conducted to study the thermal decomposition behaviors of IOS, showing that 550 degrees C might be the pyrolysis final temperature. A explanation of the heat-mass transfer process was presented to demonstrate the influence of microwave-assisted pyrolysis on the liquid product distribution. The heat-mass transfer model was also useful to explain the increase of liquid product yield and heavy component content at the same heating rate by two different heating methods. Experiments were carried out using a fixed bed reactor with and without the microwave irradiation. The results showed that liquid product yield was increased during microwave induced pyrolysis, while the formation of gas and solid residue was reduced in comparison with the conventional pyrolysis. Moreover, the liquid product characterization by elemental analysis and GC-MS indicated the significant effect on the liquid chemical composition by microwave irradiation. High polarity substances (epsilon > 10 at 25 degrees C), such as oxy-organics were increased, while relatively low polarity substances (epsilon < 2 at 25 degrees C), such as aliphatic hydrocarbons were decreased, suggesting that microwave enhanced the relative volatility of high polarity substances. The yield improvement and compositional variations in the liquid product promoted by the microwave-assisted pyrolysis deserve the further exploitation in the future. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.