This paper describes the assembly method of the Aeromagnetic Gradiometric System which can be used not only in horizontal (including transverse and longitudinal plane) but also in vertical gradient survey on the Y-5 fixed-wing aircraft with the single engine and the double wings. The method and the results of applying AADCII Automatic Aeromagnetic Digital Compensator are also preliminarily discussed. Repeated tests prove that this compensation method is very effective.