Body Sensor Network (BSN) incorporates biomedical engineering technology and wireless sensor network and has characteristics such as miniaturized size, low power consumption, easy and safe operation. It can monitor human physiological information and movement information in real-time and provide versatile vital quantitative information. This paper primarily describes BSN and its application in mobile healthcare, such as human gesture acquisition, fall detection, and recovery training. We also have implemented a body inertial-sensing network for gait analysis of hemiplegic patients.