Mobile phone detector is a kind of equipment that emits fundamental wave signal, receives the second, third or even higher harmonic/combined wave signal radiated by the target, and judges, identifies and detects the target mobile phone. Compared with the equipment for locating cell phone signals, the cell phone detector can not only get the fundamental channel information from the target, but also get 2, 3 times or even higher information, which can be detected whether the cell phone is turned on or off. Its main detection objects are metal nodes and PN junctions in mobile phones.