In the process of single screw extrusion molding， the materials are easily affected by process conditions， which leads to self-degradation and heat release， thereby posing potential safety hazards. So quantifying the decomposition heat release of materials during the extrusion process has practical significance. The experimental and simulation methods were combined to investigate the thermal decomposition phenomenon of energetic materials during extrusion process based on the self-developed finite element secondary development subroutine. Combining the thermal decomposition kinetics model of materials， a thermochemical coupling method was proposed to calculate the thermal decomposition degree， temperature rise and the maximum temperature difference between inlet and outlet of energetic materials during extrusion. The influence of process conditions on the thermal decomposition degree of materials was also examined. Additionally， a material thermal decomposition experimental apparatus was built to validate the feasibility of the proposed thermal-chemical coupling method. The results show that under the condition of a screw speed of 10 r·min^-1， compared with ignoring material thermal decomposition， the highest temperature during the screw extrusion process considering the decomposition heat release of materials increased by 0.91 K， and the highest pressure decreased by 8.2%. The decomposition degree of materials is the combined effect of material temperature increase and residence time. Compared to increasing the rotational speed， raising the temperature of barrel presents a greater effect on the thermal decomposition of materials.