Abstract: The 25th solar activity peak has ushered in a period of frequent solar activities, resulting in geomagnetic storms. These storms create irregular disruptions in the global ionosphere, leading to scintillation phenomena in GPS signals passing through it. Consequently, the precision and reliability of GPS positioning services are compromised. Understanding the patterns of ionospheric scintillation disturbances driven by geomagnetic storms and their impact on GPS positioning accuracy is essential to mitigate the adverse effects of geomagnetic storms on GPS positioning. However, existing research has predominantly focused on strong solar flares (X-class), neglecting the more common low-intensity solar flares (M-class) and their interconnected effects on geomagnetism, ionosphere, and GPS positioning. This study examines the case of an M1.7-class solar flare that occurred on April 21, 2023. By analyzing observational data from solar and geomagnetic parameters, along with data from 229 GPS stations worldwide, explore the relationship between this M-class solar flare and the resulting geomagnetic storm. investigate the global ionospheric scintillation disturbances induced by the geomagnetic storm and their impact on kinematic precise point positioning (PPP) accuracy. Additionally, identify the reasons behind the decline in GPS positioning accuracy due to ionospheric scintillation in this specific case. The research reveals that the M-class solar flare triggered a severe-level geomagnetic storm. Potential causes for this intense geomagnetic storm include solar flares accompanied by coronal mass ejections, southward Interplanetary Magnetic Field (IMF) Bz, and high-speed solar wind. Geomagnetic storms in low-latitude regions result in less significant ionospheric scintillation compared to mid-latitude and high-latitude regions, primarily occurring on the nighttime side near the magnetic equator. Ionospheric scintillation induced by geomagnetic storms leads to increased cycle slip detection, reducing PPP accuracy. In low-latitude regions where geomagnetic storms do not cause ionospheric scintillation, positioning accuracy also diminishes due to elevated cycle slip detection during PPP solutions, data outage, decreased GPS measurement accuracy, and a decrease in the number of available satellites.