Abstract: Ionospheric anomaly generate negatively affect for the reliability and positioning accuracy of BDS/GNSS. Evaluating and reduction the impact of ionospheric anomaly on the observation quality of BDS/GNSS is an prerequisite for ensuring the stability of BDS/GNSS position services. In this paper, we select three ionospheric anomaly events in 2023. The performance for cycle slip detection of the MW combination and the differential GF combination is compared using pseudorange and carrier phase from four BDS GEO satellites. Meanwhile, the impact of ionospheric anomaly on the BDS /GNSS position services is evaluated using PPP static displacement. The results show that: 1) there may be undetected cycle slip for the MW combination and the differential GF combination relying on fixed thresholds, may have a weekly jump omission. 2) the positional accuracies in three components are significantly reduced, with a more pronounced effect on the elevation direction.