A head mounted system includes a physiological signal sensor, a signal processing circuit, a memory, an application processor, and an eyeglass frame. The physiological signal sensor monitors a physiological state to output a physiological signal. The signal processing circuit determines whether the physiological state is abnormal according to the physiological signal. When it is not abnormal, the signal processing circuit controls the physiological signal sensor to monitor the physiological state at a first monitoring frequency. When it is abnormal, the signal processing circuit outputs a warning signal, and controls the physiological signal sensor to monitor the physiological state at a second monitoring frequency greater than the first monitoring frequency. The application processor receives the warning signal and stores physiological data corresponding to the physiological signal in the memory. The eyeglass frame carries the first physiological signal sensor, the signal processing circuit, the memory, and the application processor.
