By analysis of a mathematic model of aircraft magnetic field, the airp lane magnetic field model was expressed by the direction cosine and its product terms. It was difficult to estimate the model parameters by using conventional m ethods due to the model collinearity, so a new compensation method using the fin ite impulse response model was proposed. The outputs of optical pumping magnetom eters and threeaxial magnetometers were used as the inputs of finite impulse r e sponse model. The bandpass filter was used to extract the variation magnetic f i eld, and the minimal variance was employed to estimate parameters of the finite impulse response model. The airplane magnetic field data was obtained by using p arameters of finite impulse response model. The total magnetic field data subtra cted by the airplane magnetic field data gives the detected object magnetic data . Finally, the method was validated by a computer simulation.