The magnetic field caused by Equatorial Electrojet (EEJ) only occupies a small part of the geomagnetic field recorded at Earth surface or at satellite orbit, but its daily variation can be up to hundreds nT in equatorial zone as in Vietnam and affects strongly to the geomagnetic field measurements. Previously, studies of EEJ mainly used the geomagnetic field data recorded at the observatories. Today, dozens of satellites measuring geomagnetic field gave us a lot of data to study EEJ on a global scale but using such satellite data have not been fulfilled in Vietnam.