In order to reveal the reasons of forming pore in hydroxyl terminated polybutadiene/ammonium dinitramide/ammonium perchlorate/aluminium (HTPB/ADN/AP/Al) composite propellants, a series of propellant samples containing ADN and triethanolamine (TEA), triethanolamine trifluoroboron complex (T-313), tris(2-methylaziridinyl)phosphine oxide(MAPO), isophthaloyl-bis-(2-methylaziridine) (HX-752) were prepared, and the components of reacting with ADN and forming pore were confirmed,and the reaction mechanism was analyzed by DSC/TG-IR/MS. Results show that there are no pores in the propellant samples containing curing agents such as toluene diisocyanate(TDI), isophrone diisocyanate(IPDI) and ethanolamine bonding agents such as TEA,T-313 respectively, but the pores are formed in the samples containing aziridine bonding agents MAPO and HX-752. It is proved by DSC that there is a strong interaction between ADN and MAPO, which decreases the temperature of the main decomposition peak of ADN by about 99.7 ℃. When the mixture of ADN and MAPO (mass ratio 1:1) was heated continuously at 50 ℃ for 2 h, the gasous products N₂O and NO₂ are formed and detected by mass spectrum. It is considered that the aziridine bonding agents can accelerate the decomposition of ADN, which form pores in the propellants.