The brain magnetic fields evoked by acupuncturing LI-4(Hegu) were measured by using SQUID (superconductive Quantum Interference Device) Biomagnetometer, and the morphological characters of these biomagnetic fields were examined in 12 subjects. The observed phenomenon of the LI-4(Hegu)'s projection area overlapping on the jaw's and face's projection area suggests that excitation of LI-4 (Hegu)'s projection area activated by acupuncturing LI-4(Hegu) could inhibit action of the jaw's and face's projection through the overlapping area, and this is the reason why the acupuncturing LI-4(Hegu) could effectively case pains in the treatment of dental pain.