In order to study the initiate mechanism of pulse detonation engine ignited by low temperature plasma through numerical simulation method, the low temperature plasma ignition discharge area was simplified into heat kernel with high temperature and high pressure considering the propane/air chemical reaction kinetics mechanism. The laminar finite-rate model in the FLUENT was used to simulate the combustion process from deflagration to detonation transition (DDT) initiated by low temperature plasma, and the process was analyzed minutely. The experimental results show that it is feasible to simplify the low temperature plasma ignition to the fire kernel of a certain pressure and temperature in numerical simulation under a reasonable boundary condition that the pressure is atmospheric pressure and the wall temperature is normal temperature. The ignition delay and measurement error results in that the detonation wave development time of the numerical simulation is shorter than that of experimental result. The measurement value of the experiment is close to the result in numerical simulation under the condition of normal pressure heat kernel and normal temperature wall.