A detection device and an indoor navigation system are provided. The detection device includes two detection modules each including a sound receiver for receiving sound from a peripheral object and a signal converting circuit that is electrically coupled to the sound receiver and that is configured to convert input signal from the sound receiver into a target spectrogram. The two spectrograms from the signal converting circuits have a time/phase difference, and at least one wireless earphone includes a storage unit and a judging circuit that is electrically coupled to the storage unit and the two signal converting circuits. The judging circuit is configured to compare any target spectrogram with basic spectrograms of the storage unit so as to determine which kind of objects the peripheral object is, and is configured to obtain an instant position of the peripheral object by the time/phase difference.