Abstract: The fast polarization modulation and the ultra-narrow-band filtering both are the key tools for solar telescopes to detect the magnetic field. The liquid crystal modulation is, up to now, the only electro-optic modulation technology that can meet the requirements of the polarization measurement and the narrowband filtering at the same time. Moreover, the liquid crystal modulator enjoys many advantages, such as the large aperture, the wide spectral range, the fast modulation speed, without a rotation mechanism and the continuously adjustable phase delay, which make the liquid crystal modulator a strong growth point of the magnetic field detection technology for the next generation of solar telescope. This paper briefly introduces the development history, the basic working principle of the liquid crystal, the current applications of the liquid crystal modulating technology in the solar magnetic field telemetry, and the challenges and the future development directions of the liquid crystal modulation technology. As seen from the research and development of the solar magnetic field telescopes in China, it is believed that the liquid crystal modulation technology will play an important role in the space- and ground-based solar magnetic field detection in the future.