Abstract: In order to study the metrical problems in gas injection wells and production wells for the vertical distance in SAGD(steam assisted gravity drainage),the alternating magnetic field generated in the fluxgate sensor rotary magnetic beacon was applied to calculation the distance.Three axis fluxgat sensor output values were used to calculate the vertical distance between the two holes,and kept the distance between the first and second boreholes within a certain range,thus effectively made wells keep parallel.In order to compensate for the effects of perturbing magnetic fields associated with magnetized sections of the drill collar,a correction method of determining the distance which relied on the knowledge of local geomagnetic field and interference magnetic field was described in detail.The measuring experiments show that the correction method can determine an accurate vertical distance under the environment of the disturbance of magnetic material.It is simple,effective and practical,and beneficial to improving the recovery of oil resources.