Pyrolysis technology holds significant potential for the harmless, resourceful, and reduced disposal of sludge in pulp and paper mills. Currently, the understanding of the thermal behavior, thermodynamic characteristics, and product composition during the pyrolysis process of sludge from pulp and paper mills remains incomplete. In this study, thermogravimetry-fourier transform infrared (TG-FTIR) technology was employed to investigate the thermal behavior and real-time release characteristics of volatile products for pulp and paper mill sludge pyrolysis at different heating rates. Additionally, a multi-component parallel reaction kinetics model, kinetics compensation effect, and master plot method were used to explore the pyrolysis kinetics of organic compounds. The results indicated that the thermal decomposition of organic matter in pulp and paper sludge was primarily concentrated in the temperature range of 140-600 ℃. The pyrolysis products mainly included H_2O, CH_4, CO_2, CO, NH_3, ketones, aldehydes, carboxylic acids, phenols, aromatics, ethers, and alcohols. As the pyrolysis temperature increased (600-900 ℃), CaCO_3 in the pulp and paper sludge decomposed, producing a large amount of CO_2, and simultaneous reactions occurred between CO_2 and pyrolytic carbon to generate CO. The parallel reaction kinetics model with four components could effectively describe the organic decomposition process of pulp and paper sludge. The average apparent activation energy for the four pseudo-components were 171.54, 179.50, 192.05, and 200.86 kJ/ mol, with pre-exponential factor ranging from 1.74×10^11-8.34×10^16, 1.47×10^11-5.55×10^13, 1.40×10^11-1.55×10^12, and 1.67×10^10-1.34×10^13 s-1, respectively. Different reaction mechanism models were followed among the various components, and the reaction mechanism models were changed with increasing conversion fraction.