An electronic device and a method for sensing an active state of an object are provided; the electronic device includes a signal generating module, a non-symmetric antenna module and a signal analyzing module. The signal generating module is configured to generate a pulse width modulation signal, generate a measuring signal with overshoot and undershoot pulses according to the pulse width modulation signal, and generate a reference signal according to the measuring signal. The non-symmetric antenna module includes a transmitting antenna and a receiving antenna. The transmitting antenna is configured to transmit the measuring signal to an object. The receiving antenna is configured to receive the measuring signal reflected by the object. The signal analyzing module is configured to receive and process the reference signal and the measuring signal reflected by the object, so as to obtain an object active state signal.