Abstract: The Galinger iron polymetallic orefield is located Gobi desert, covered by Quaternary layer of 120 -200 meterthick.After the drilling project, three-component magnetic survey in boreholes is the most direct way to search blind orebodies in the bottom ofor nearby the holes.Based on the analysis of thethree-component borehole magnetic surveydata in the Galinger orefield, the authors research thechange rule of ΔZ and ΔH'curves and ΔT'vector.In the seeking oforebodies around the borehole and in the deep, this method is effective to guidethe distribution of drill holes scientifically and promote the probabilityof positive drill hole.