Abstract: Basing upon the even function (the cosine series) in this paper is introduced a method including the total field reduced to the pole and its second derivative and the continuation for numerical processing of aeromagnetic data. The method presented here is much more accurate than that of the Fourier method, while the boundary effect is depressed to a certain degree. In addition, an example utilizing the method also shows it to be useful for the exploration of mineral deposits and study of geologic structures of the deep-seated crust. Finally, the computer program of the method is presented. By combining the Fast Fourier Transforms (FFT) with the recurrence process applied in the program, the computation time is shortened and the amount of data is less restricted.