Ammonium nitrate (AN)-based composite propellants have several major problems, namely, a low burning rate, poor ignitability, low energy, and high hygroscopicity. The addition of a burning catalyst proved to be effective in improving the burning characteristics of AN-based propellants. In this study, the burning characteristics of AN-based propellants supplemented with MnO2 as a burning catalyst were investigated. The addition of MnO2 is known to improve the ignitability at low pressure. The most effective amount of MnO2 added () for increasing the burning rate is found to be 4%. The increasing ratio with is virtually independent of the burning pressure and the AN content. However, the pressure exponent unfortunately increased by addition of MnO2. The apparent activation energy of the thermal decomposition for AN and the propellant is decreased by addition of MnO2. From thermal decomposition kinetics it was found that MnO2 could accelerate the thermal decomposition reaction of AN in the condensed phase, and therefore, the burning characteristics of the AN-based propellant are improved.