Abstract:The higher-order ionospheric(HOI) delays for GPS, GLONASS, Beidou and Galileo in three MGEX stations at different latitudes in different solar and geomagnetic conditions are calculated. Moreover, effects of HOI on multi-GNSS precise point positioning (PPP) are studied and the impact of different solar and geomagnetic activity on the accuracy of PPP is demonstrated. The results show that higher-order ionospheric delay decreases with increasing latitude. Solar activity is the main factor to affect the higher-order ionospheric delays. The second-order ionospheric delay is less than 2 cm and the third-order ionospheric delay is about 1 mm at low solar activity. The second-order ionospheric delay is more than 2.5 cm and the third-order ionospheric delay reaches 5 mm at high solar activity. When a geomagnetic storm occurs, the delay has a certain degree of growth. After correcting the higher-order ionosphere delay, the improvement effect of positioning accuracy is better at lower solar activity than at higher solar activity.