To investigate the effect of potassium chloride(KCl) on the detonation performance and thermal stability of ammonium nitrate(AN), modified AN containing KCl was prepared via, solution mixing method and mechanical mixing method. The detonation performance and thermal stability of AN/KCl mixtures were investigated by differential scanning calorimetry(DSC), accelerating rate calorimeter(ARC), the United Nations(UN) gap test and Koenen test. Results show that the exothermic peak temperature of modified AN containing 10% KCl obtained by solution mixing method was decreased from 286.75 ℃ to 250.84 ℃, while the onset temperature of modified AN was increased from 204.33 ℃ to 220.17 ℃, revealing that KCl can promote the thermal decomposition process of AN and doesn't affect first step of the thermal decomposition of AN. The detonation test results show that KCl can reduce the thermal sensitivity of AN and the detonation propagation ability to a certain extent. Compared with mechanical mixing method, to suppress the detonation of AN, the amount of KCl required can reduce by 20% for solution mixing method. The mixing method has an important effect on the detonation characteristics of AN.