Abstract: A detailed north-south section around the meridian at 120E of seasonal variation of Sq(H) for quiet days are presented using the data of ten geomagnetic observatories with nearly equal separation in latitudes between stations in eastern China,with the method of main component analysis. The apparent focus latitude of the equivalent current system in the ionosphere is presented. It is shown that the variation of 2 for Sq(H) is resulted from the deviation of the axis of symmetry of the equivalent current system from the geomagnetic axis.