A theoretical model of temperature for Al2O3 ceramics during micro-detonation of arc strike machining was established. Based on finite element theory, the temperature of Al2O3 ceramics during micro-detonation of arc strike machining was simulated with the aid of Ansys software, combined with the actual processing, the width and depth of cavity impacted by micro-detonation were calculated. The simulation results show that the highest temperature of Al2O3 ceramics is over 13435 °C in a given processing parameters, while the high-temperature zone is quite small. With the increase of pulse width and electricity, the temperature within the machined zone increases rapidly, but the outside area kept a low temperature; and with the increase of nozzle radius, the diameter to depth ratio of the distribution of temperature is increasing gradually. The data gained from the simulation is proved to be accordant with the data gained from experiments.