Abstract: Since the introduction of the general airgap filed modulation theory (GAFMT) by the author's team in 2017, it has become a hot spot within the area of electrical machine, due to its advantages in principle analysis, performance calculation, and topology innovation. In 2019, it was funded as a major project by the National Natural Science Foundation of China titled "Magnetic field modulation theory and design methods for high-quality servo motor systems". After 5 years of in-depth research, numerous original achievements have been made in the magnetic field modulation mechanisms, mathematical representation methods for field modulation and other relevant areas. This paper comprehensively reviews the latest research advancement in the GAFMT from three aspects: theory, technology, and application. It includes the proposition of magductance and hysteretance modulators, the extension of modulation modes to include frequency modulation, amplitude modulation and phase modulation, the introduction of a multi-working harmonics design concept based on "fundamental + harmonics", and the demonstration of the relationship between the GAFMT and traditional electrical machine theory. Finally, it offers prospects for future research and development directions of the GAFMT.