Abstract: Objectives: Although infrequent, strong earthquakes (M_w ≥ 6.0) can be extremely destructive and occur on subduction and intraplate faults worldwide. Exploring the reliability and timeliness of the high-rate GNSS continuous stations for rapid inversion of slip distribution and rapid estimation of earthquake magnitude during strong earthquakes, as for the Anninghe fault with high potential for strong earthquakes, has important practical significance for earthquake early warning in this region. Methods: In view of the limited number of strong earthquakes and few high-rate GNSS stations, synthesizing 1100 M_w 6.5–7.5 earthquakes events or rupture scenarios along the Anninghe fault based on the kinematics numerical simulation method of coseismic rupture with the interseismic locking model as a priori constraint, and simulating displacement waveforms with random noise signals at existing or new-built GNSS stations. These waveforms were analyzed and discussed the reliability of fault slip distribution along the Anninghe Fault in combination with the steepest descent method. Results: For the M_w 6.5–7.5 earthquakes along the Anninghe fault, where GNSS stations are dense, the initial inversion magnitude (M_w 6.2) can be determined about 8 s after the earthquake using the existing GNSS continuous stations, and accurate magnitude estimates and slip distribution results can be obtained within a short time or before the rupture is completed. The GNSS continuous stations of the China Earthquake Science Experimental Field, which is about to be built, can effectively obtain the magnitudes and slip distributions, and even more effectively describe the dominant direction of fault rupture. Conclusions: Our findings confirm the feasibility and usefulness of using high-rate GNSS data in magnitude estimation and finite-fault slip inversion of strong earthquake along the Anninghe fault, will provide theoretical basis and technical support for earthquake early warning in this region.