<p>Vector magnetic measurement is increasingly widely used. In order to improve the accuracy of vector magnetic measurement system on board a vehicle, researchers have proposed various calibration methods. Most of them require altering the magnetic vector in the vehicle coordinate system. Exploring the use of geomagnetic variation to change the geomagnetic vector in the vehicle coordinate system, this paper proposes a novel vector magnetic measurement calibration method. In this method, a vector magnetometer mounted on a vehicle and an accurate vector magnetometer separately measure the geomagnetic field at different locations within the same area. Based on the physical principle that the geomagnetic variation at two nearby locations is equal, the calibration parameters of the magnetometer on the vehicle can be determined through a set of equations containing the measurements from the two magnetometers. The theoretical derivation and simulation experiment results demonstrate the feasibility of this method. Therefore, it can serve as a new alternative calibration method, especially in scenarios where a high degree of accuracy in the estimation of calibration parameters is not required.</p>