Under the dual carbon goals, coordinated governance of air pollution is the key to promoting the comprehensive green transformation of industry. Papermaking sludge undergoes complex physical and chemical transformations during the coordinated disposal of industrial kilns, producing NOx and other pollution. Exploring the generation mechanism of NOx in the process of coordinated disposal of papermaking sludge by industrial kilns and analyzing the form and migration characteristics of its nitrogen-containing functional groups can provide new ideas for controlling NOx pollution emissions. In this paper, the transformation and migration of nitrogen-containing functional groups in papermaking sludge and pyrolysis at different temperatures were analyzed by means of nuclear magnetic resonance (NMR) analysis and gradient temperature inversion method. The results show that the release of nitrogen-containing functional groups is mainly concentrated in the temperature range of 250 ℃ to 300 ℃. From 200 ℃ to 250 ℃, imine and R3C—N, RCH2—N are released; from 250 ℃ to 300 ℃, thiourea, R2CH—N, RCH2—N, R3C—N are released; from 300 ℃ to 350 ℃, CH3—N, carbodiimide and cyanate are released; from 350 ℃ to 400 ℃, thiocyanate, isocyanate and CH3—N are released. TGA/DSC curve analysis further confirm the release of these functional groups, providing a reference for further environmental governance and process optimization.