Through a comparative analysis of aeromagnetic data, detailed ground magnetic data, drilling validation data and regional gravity data obtained from the Sigezhuang work area of Luannan County in Hebei Province, this paper has made a preliminary summary of characteristics and regularity of the gravity and magnetic field in deep buried iron ore deposits. In practice, the authors actively explored Jidong metamorphosed sedimentary iron deposits with the purpose of looking for deep concealed large ore deposits based on new ideas and new methods, and the result obtained has great significance in search for deep and blind iron ore deposits in the future.