The structural and electrical parameters of leakage inductance transformers can significantly affect the efficiency, noise, and vibration of microwave ovens. The paper proposed a new iron core structure with finite element modeling and simulations of a leakage inductance transformer by both the electromagnetic field and system design simulation software. Different silicon steel sheet models were used for the upper and lower parts of the proposed iron core to reduce the loss and heat of the leakage inductance transformer. The iron core scheme was changed from the traditional E-I type to the E-E type. The feasibility of the new iron core scheme was tested by numerical results which showed that the maximum temperature rise of the leakage inductance transformer decreased significantly.