A new magnitude scale relationship based on GPS peak geodynamic displacement(PGD) is constructed by synthesizing the magnitude formula of seismology and the results of current continuous GPS research on magnitude scale, using the peak geodynamic displacement data of 17 high-rate GPS stations with seismic events between M_W5.9 and 9.1 at home and abroad. According to the newly established relationship and the actual data analysis, it is considered that the magnitude scaling relation of GPS peak geodynamic displacement is suitable for magnitude calculation of larger earthquakes with M_W ≥ 5.6, and the applicable range of focal distance for earthquakes with different magnitudes can be derived. This paper also presents that a wider range of the scaling relationship for estimating earthquake magnitude based on high-rate GPS' PGD can be obtained by using site correction, source radiation and propagation path correction.