Abstract: For investigating the pyrolytic characteristics and mechanism of spent mushroom substrate, this research studies the thermogravimetric (TG) curve and differential thermogravimetric (DTG) curves of spent mushroom substrate (SMS) of Shiitake mushroom at different heating rates, using the combination of thermogravimetry and thermogravimetry-infrared the pyrolysis in nitrogen atmosphere. A peak splitting technique was used to analyze the DTG curve, thereby to calculate the activation energy E, reaction order n, frequency factor A, further to obtain the precipitation characteristics of the pyrolysis products. A pyrolysis experiment at constant temperature for SMS of Shiitake mushroom was performed on a fixed bed, where the experimental temperatures were set at 500, 550, and 600 ℃, thereby to analyze the yield and composition of three-phase products. Industrial analyzers were used to characterize and compare raw materials and pyrolysis semi-coke, where the FTIR was used to perform functional group analysis on semi-coke, the GC-MS was used to analyze pyrolysis tar, and a flue gas analyzer was selected to measure pyrolysis gas online. The results showed that the pyrolysis of SMS of Shiitake mushroom can be divided into three stages: the water precipitation, the pyrolysis, and the carbonization stage. The pyrolysis stage dominated during the entire process with the temperature range of 250-550 ℃, where the weight loss reached 58%. There was no obvious effect of heating rate on pyrolysis. Nevertheless, the TG and DTG curves of the sample shifted to the high temperature zone, as the heating rate increased. The apparent activation energy for the pyrolysis of SMS of Shiitake mushroom was 66.33 kJ/mol, easier for pyrolysis due to the low apparent activation energy. In the pyrolysis experiment performed on the fixed-bed at constant temperature, the main components of the pyrolysis gas of SMS of Shiitake mushroom were CO2, CO, CH4, H2, ranking in order: CO2, CO, CH4, H2, which was well consistent with the measured data from the TG-FTIR. At 600 ℃, the contents of CO and H2 increased significantly. The data of gas analysis showed that the overall gas yield of the reaction was well consistent under the experimental conditions, indicating that the pyrolysis reaction was fully completed. At 500 ℃, the liquid products of pyrolysis were mainly silicon-containing organics, showing that there was a certain amount of silicon in the raw material. The main component of the bio-oil from the pyrolysis of the mushroom residue was CxHyOz, as the pyrolysis temperature increased, indicating a promising potential application using the pyrolysis of mushroom residue to produce the bio-oil. In the semicoke from the slow pyrolysis of mushroom residue, the dominated component was fixed carbon, compared with the raw material, indicating the proportion of volatile contained in pyrolytic semicoke decreased significantly. There was no significant difference in the types of functional groups in the pyrolysis semicoke at the three temperatures, whereas, there were obvious characteristic peaks of alcohols, carboxylic acids, and aromatic groups.