Abstract: The exothermic reaction behavior of TBP with nitric acid and 30%TBP-70% n-dodecane with nitric acid was studied by adiabatic accelerating calorimeter. The influence of the diluent on the exothermic reaction was determined by the comparison and analysis of the two series of test results. The results show that the higher the concentration of nitric acid, the lower the onset temperature of the self-exothermic reaction of TBP or TBP-n-dodecane and nitric acid, the higher the heat release and the pressure increase. Under adiabatic conditions, the presence of diluent n-dodecane exacerbates the exothermic reaction, resulting in lower reaction initial temperature, lower activation energy, and higher energy release.