Abstract: Precise point positioning real time kinematic (PPP-RTK) enables fast and precise positioning with the precise atmospheric corrections from the regional network, and it is regarded as the technology of choice for autonomous driving. However, PPP-RTK is hardly maintaining stable and reliable positioning result under ionospheric scintillation which has become one of the major challenges for PPP-RTK. In this contribution, the PPP-RTK model and ionospheric scintillation characteristics are introduced. The impact of ionospheric scintillation on PPP-RTK is analyzed in four aspects: observation quality, circumferential hop detection, atmospheric products and positioning performance based on the GNSS observations from the Hong Kong Satellite Positioning Reference Station Network. The results show that ionospheric scintillation reduces observation quality and increases the probability of wrong cycle slip detection. The accuracy of the corrections of GPS, Galileo, and BDS decreased by 64.7%, 64.0%, 247.5%, respectively, and the number of which decreased by 4.5. Finally, the positioning accuracy of PPP-RTK is increases by 11.8 times compared with the normal period, and the fixing percentage is reduced by 55.76%. The GEC mixed solution can significantly improve the positioning performance, of which the positioning accuracy in improved by 93.06% and the fixing percentage is increased by 51.88% compared with the GPS-only solution.