Abstract: The number and exposure of active sites can significantly affect the catalytic performance of catalysts in heterogeneous catalysis. Atomically dispersed catalysts are a good choice for heterogeneous catalysts due to their fully exposed active sites and superior catalytic efficiency, which are expected to play a good role in the typical heterogeneous catalytic reaction of ammonium perchlorate (AP) thermal decomposition. A series of graphitic carbon nitride (CN)-supported cobalt atomic-level dispersed catalysts SACo-CN-X with different cobalt loadings were fabricated by using pyrolysis method, and the structure was analyzed by FT-IR, XPS and AC-STEM. The results show that SACo-CN-X inherits the characteristics of CN framework, and Cobalt species are highly dispersed and anchored in CN substrate mainly in the form of Co-N_x. The Cobalt mass fractions of SACo-CN-1, SACo-CN-2 and SACo-CN-3 are 1.34%, 2.41% and 3.65%, respectively. The catalytic performance increases with Co introduction amount. In particular, 5% SACo-CN-3 reduces the main decomposition peak of AP from 431.2 ℃ to 292.5 ℃, with a decrease of 138.7 ℃, while the actual Co mass fraction in the reaction system is lower than 0.2%. TG-IR results show that the NOCl content decreases and NO₂ maintains high proportion in the SACo-CN-3 catalytic system, indicating that Co-N_x sites promotes the cleavage of HClO₄-related intermediates and the oxidative conversion of nitrogen-containing intermediates. The apparent activation energy calculated by the Ozawa method is about 42~67 kJ·mol⁻¹. These results indicate that highly dispersed Co-N_x sites anchored by the CN framework can effectively lower the energy barrier of AP decomposition at low Cobalt dosage, providing a catalyst design strategy for regulating AP thermal decomposition.