In order to research thermal behavior of benzoyl peroxide(BPO) mixed with NaOH solution, dynamic and isothermal experiments were carried out by differential scanning calorimeter (DSC). Thermal safety software(TSS) was used to analysis thermal behavior. Two methods were established to obtain reaction thermodynamic parameters, model-free method(Friedman method) and model-based method. By Friedman method, the activation energy of BPO with NaOH solution changed greatly, which demonstrated that the reaction was a multi-step reaction. By model-based method, BPO with NaOH solution can be described as A -> B -> C, where the first step A -> B is an autocatalytic reaction, the second step B -> C is a n-order reaction. Finally, the self-accelerating decomposition temperature(SADT) was predicted and the result indicated that SADT of BPO with NaOH solution is -1 degrees C, which is much lower than BPO.