An atmospheric pressure microwave plasma torch(MPT) operating at 2.45 GHz was designed. Corresponding simulation based on HFSS code was performed and the influences of structure parameters on the E-field distribution in the device were analyzed. The results indicate that the use of coupling probe will have a distinct impact on the field distribution in the device. A MPT with strong electric field amplitude and high Q-factor about 20 000 was achieved in simulation by adjusting the structure parameters, which could produce microwave plasma at atmospheric pressure.