Abstract: The influence of solar and geomagnetic activities on electrical propulsion system of ultra-low orbit gravity satellite was evaluated for the current 25^th solar cycle. The orbit simulation was carried out and the data of GOCE mission was analyzed. The variation of atmospheric drag was analyzed. The influence of solar activity on propellant consumption and the influence of geomagnetic storm on drag-free operation were obtained. The results show that the orbit altitude of the satellite in the low solar activity years can be reduced by about 20 km compared with that in the high solar activity years, which is conducive to improving the gravity signal intensity. Strong geomagnetic storms usually increase the drag by 30% to 90% at ultra-low orbit, so thrust margin is required for geomagnetic storms. Designer should ensure high specific impulse in thrust range of 10% to 70% of the maximum thrust. The life consideration of this range is important.