The invention provides a detector used for power distribution equipment inspection and live-line detection. The detector comprises a composite sensor, a preposed processing unit, a thermal image collection unit, a map analysis unit and an analysis control and communication unit which are connected in sequence. The composite sensor is composed of an ultrasonic sensor, an earth electric wave sensor and an infrared thermal image sensor and is used for collecting signals and converting the signals into analog electric signals. The preposed processing unit is used for carrying out filtering, amplification and denosing processing on the analog electric signals. The thermal image collection unit synchronously obtains the processed analog electric signals and forms mixed digital codes according to preset collection parameters and signal coding rules. The map analysis unit decodes the mixed digital codes and forms a visual partial-discharge positioning thermal image spectrogram. The analysis control and communication unit displays the thermal image spectrogram and outputs the thermal image spectrogram to external equipment. According to the invention, comprehensive evaluation is carried out based on detection data of a plurality of kinds of detection methods, the misjudgment rate of the detection result is lowered, the detector is convenient to carry, and the difficulty of live-line detection work is lowered.