Tolles-Lawson（ T-L） equation is widely used in aeromagnetic interference compensation

in model

the geomagnetic field is set to a constant value. But in practice

there is a gradient in the geomagnetic field

and the compensation precision will be affected. To solve this problem

the gradient variation of geomagnetic field is considered in the traditional T-L model

and the parameter estimation and compensation formulas of the unsteady geomagnetic field are derived. According to the relationship between forward flight and anti-flight disturbance magnetic field under the same flight path

the magnetic gradient can be corrected

and then the measured data can be brought into the model to compensate

and the high-precision magnetic field measurement value can be obtained. The simulation results show that the mean standard deviation decreases from 0. 142 3 n T to 0. 080 2 n T and 0. 182 7 n T to 0. 066 5 n T

respectively

in the case of linear and non-linear geomagnetic gradients

which proves that the improved model has better compensation effect for magnetic interference.