Ammonium perchlorate(AP) and LiBH4 can form an oxidation-fuel energetic system, which provides a new development direction in designing novel mixed explosive formula. The microcalorimetry and self-designed slow cook-off setup were used to study thermal performance of AP/LiBH4 energetic powders and grains respectively. Experimental results show that heat release in microcalorimetry method for the mixed system at low temperature was due to the reaction between LiBH4 and residual water vapour. The oxidant gases from AP decomposition participate in the oxidation of LiBH4 at high temperature. The ignition temperature for the AP/LiBH4 grain was 270 degrees C and the explosion reactions were violent in slow cook-off test.