The pressure differential scanning calorimetry (PDSC) was used to an investigation of the interaction of potassium salt flame suppressors with trimethylotethane reinitiate (TMETN) and burning catalyst used in NC/TMETN insensitive propellants during thermal decomposition. The data from thermal analyses show that there is an obvious interaction during thermal decomposition of the mixtures of potassium salt with Pb-Cu-CB catalyst and TMETN. Among three kinds of potassium salts, K₃AlF₆ has a destructive action for catalyst lead phthalate (Φ-Pb) decomposing into active component PbO. This may be one of the reasons that K₃AlF₆ make the propellant plateau effect disappear.