A potassium 5, 5′-azotetrazolate(PZT) was synthesized through alkaline oxidation reaction using 5-aminotetrazole as a starting material. The structure of PZT was characterized by IR and elemental analysis and then the molecular formula C₂N₁₀K₂·3H₂O was confirmed. Thermogravimetry and differential scanning calorimetry results show that endothermic reaction occurs and PZT loses crystal water from 315 K to 350 K. The maximum exothermic peak appears at 539.3 K. As flame inhibitor used in gun propellant charges at following: initial velocity 912 m·s^-1, pressure 279.4 MPa, PZT content 2%, the effects of PZT on muzzle flame and smoke were tested by high speed photography method and a smoke box method. Results show that the flame area decreases by 71.4% and the flame temperature reduces by 400 ℃ when PZT used instead of the common flame inhibitor K₂SO₄. The high-nitrogen flame inhibitor PZT has better effect in reducing muzzle flame and smoke than K₂SO₄.