Objective: To investigate the electromagnetic field and specific absorption rate(SAR) distribution of different structure applicators with different depths for treating bone tumors using microwave hyperthermia. Methods: The finite element method ( FEM ) was used to calculate dectromagnetic field and SAR distribution. Two different structure applicators were simulated. The one is simple coaxial antenna, which has been successfully used in clinic treating bone tumors in Tangda hospital of the Forth Military Medical University several years. It was formed by a coaxial cable peeled off the out copper at end. The other applicator was coaxial-slot antenna, which was widely used in microwave hyperthermia. The applicator inserted into the cylindrical bone with different depths, and worked at the frequency of 2 450 MHz. Results: The electric field and SAR generated by the simple coaxial applicator were mainly concentrated out the tissues, and were not uniform in the tissues, while the coaxial-slot applicator well transmits the electric field and SAR into the tissues, and can easily treat different position by adjusting the slot position. Conclusion:The results calculated by EFM, were well accordant with the experimental and clinical results, and will be important for improving the clinical effects of microwave hyperthermia.