Using IGRF(International Geomagnetic Reference Field) workout by IAGA (International Association of Geomagnetism and Aeronomy), this paper investigates the geomagnetic field in the 20th century.

• 利用IAGA(国际地磁与高空物理学协会 )编制的IGRF(国际地磁参考场 )研究了 2 0世纪地磁场变化规律 .