Abstract: In this paper, based on the spherical harmonic model of the geomagnetic field, the spherical harmonic expressions of the vertical gradient of the geomagnetic field are given. The grid values of the geomagnetic field and its vertical gradient at 0.50, 100km above sea level are calculated. The contour maps of the vertical gradient of total intensity, vertical intensity, horizontal intensity and declination are drawn. The geographical distribution and change with height of the vertical gradient of the geomagnetic field are analysed.