With the development of biomedical field, wireless implantable devices are playing an increasingly important role. Taking into account the power loss and specific absorption rate (SAR) of electromagnetic waves in human tissues, the selection of frequency for implantable electrodes is of great significance. To address this issue, CST software is used to build a high-precision voxel model of the human head, simulate and explore the transmission characteristics of electromagnetic waves in the commonly used human communication frequency band of 400 MHz~6.5 GHz in the head tissue, analyze the distribution of electromagnetic fields, power density losses, and radiation hazard SAR values. The results show that the path loss of electromagnetic waves in human head increases with the depth of the tissue, and the channel loss in the frequency band below 3.5 GHz is smaller, which power density decreases less than 10 dB in the tissue within 25 mm of the skin. The human tissue has different absorption capabilities for different frequencies of electromagnetic radiation, and the SAR value of high-frequency electromagnetic radiation is generally smaller than that of low-frequency electromagnetic radiation. Among them, the SAR of 1.8 GHz reached the maximum value of 1.71 W/kg. Considering the power loss and electromagnetic radiation hazards, the optimal operating frequency for implantable brain electrodes varies with the depth of implantation. 2.45 GHz electromagnetic wave is suitable for implantable electrodes in the subcutaneous tissue within 5 mm of the head, and 1.8 GHz and 400 MHz are the optimal frequencies for implantable electrodes located 15 mm and 25 mm beneath the skin, with the power density increasing by 9.6% and 77.4% compared to 2.45 GHz.