Wireless body area network (WBAN) can provide a wide range of applications (e.g. non-medical service / Patient's urgent state monitoring system.). So we need to design the high-efficient MAC layer to improve the transmission efficiency of wireless body area networks. On the other hand, when the emergency situation appearing, a priority MAC mechanism can send the emergency information to the service at first and also can make sure that emergency information arrived. This thesis presents the Energy Saving MAC Mechanism for wireless body area networks using on-body device. Thus, when patients have an emergency situation allows sufficient support time and medical treatment time for patients. The simulation based on NS-3, in the performance evaluation, our Hybrid Priority MAC has the good performance and usability. Therefore, my research in this area has high practical significance. The WBAN (Wireless Body Area Network) technology is still in its primitive stage and is being widely researched. This technology once accepted and adopted is expected to be a breakthrough invention in healthcare leading to concepts like telemedicine and mHealth becoming real. In the WBAN, each kind of application aspect, regarding patient’s guardianship, disease’s prevention and the treatment is most essential. The modern science’s and technology’s development because the WBAN’s application becomes diversifies. The Smart wireless electrocardiography (ECG) patch, Body area network for wireless sleep staging, Body area network for monitoring autonomic nervous system responses and Autonomous wireless EEG monitor has already obtained the practical application. © Research India Publications.