Abstract: The three-axis magnetometer and its assembled the gradiometer play an important role in the satellite geomagnetic navigation and space exploration, therefore, they must be calibrated before they are put into use. This paper firstly analyzes the source of the measurement errors of the three-axis magnetometer and the gradiometer, then establishes a correction model for the measurement error. With the comprehensive coefficient method, which works without the need of considering each influencing factor, a non-magnetic turntable is used to calibrate the Bartington three-axis magnetometer and the corresponding gradiometer in the uniform magnetic environment. It is shown that with the method, the maximum total magnetic field deviation of the two magnetometers can be reduced from 552.4 nT to 15.0 nT, and the maximum output deviation of the three-component gradiometer in x direction can be reduced from 3 891.5 nT to 37.2 nT, which effectively improves the reliability of the three-axis magnetic sensor in the measurement.