Reduction to the pole at low latitude based on a Wiener filtering approach of Hansen and Pawlowski have been presented. This technique have been used to reduce the aeromagnetic anomaly map of ViÖt Nam to the pole for the case of the inclination of the regional field I ³ 5^o. The maximal horizontal gradien vectors of the reduced-to-the-pole magnetic field are determined. It showed that the boundaries founded from this maximal horizontal gradien vectors seem to correspond well to the geological boundaries. This showed the important role of the magnetic data in the geologic studies and in the exploration of mineral resources.