The invention relates to the human body target positioning and tracking field, in particular to a human body infrared detection and positioning device and a method based on a wireless sensor network. The device comprises a CPU, a radio frequency module, a sensor module, an address DIP switch, a serial port and a power supply, wherein, the sensor module comprises three pyroelectric infrared sensors. The method comprises the following steps: the method for re-dividing and coding of the visual fields of a plurality of ordinary Fresnel lenses and the method which is applicable to the cluster head dynamic selection of the wireless sensor network, etc. The device and the method can be widely applied in the indoor human body target positioning and the tracking, such as, the monitoring of whether the lifestyle habits of old solitary people are normal or not, the positioning and the tracking of an invaded target in the security, etc.