This research is aimed to determine the viscosity of liquid crystals by observing the motions of ferrofluid droplets in liquid crystal hosts under external magnetic fields. The ferrofluid droplets of size 20~30 Î¼m were suspended in two plates covering the host liquid, and their motions under the magnetic field were observed with using a polarizing microscope. As the first step, three types of isotropic liquids, such as water, glycerin, and silicone oil, were employed as the host liquid. The speed of the moving droplet was much slower than the theoretical value calculated by the equilibrium between the magnetic force and the viscous force. This fact led us to one assumption, which the droplets involve the boundary layers under the magnetic field, and all results of isotropic liquids supported this fact. The main experiments of this research, using 4-cyano-4â-penthylbiphenyl (5CB), were conducted, and the result also supported the assumption above mentioned, which the new method to determine the 5CB viscosity was established. The experiments were conducted with several conditions, and unique anistropic properties of 5CB were observed with this new method. This research showed that that the new method enables us to observe anisotopic properties with the quantitate aspects.