The three-component magnetic survey in drill hole can improve the exploration accuracy of mineral body so as to direct the exploration drilling with the surface magnetic survey after detecting the anomalies near the drill hole better.The three-component magnetic survey in drill hole is also used in search for the blind orebody near or under the drill hole and in judging the shape,direction and depth of the mineral body.This paper mainly analyzes the magnetic field distribution characteristics of sphere and the laminated body,and summarizes the corresponding relationship between the characteristics of magnetic field distribution and orientations,such as location,direction of magnetization,and sloping direction.Also,the method of judging orebody direction is studied,and the spatial location of the orebody is determined.The three-component magnetic survey in drill hole is an effective method in search for the magnetic mineral body in the depth and detecting its occurrence situation.This method was applied to the ZK1102 drill hole magnetic data of an iron ore mine in Hainan,which improved the accuracy of determining the spatial location of an underground orebody.The results obtained by the authors provide a reference for drilling or reserves evaluation of magnetic orebody.