Abstract: There is disclosed an NMR cell system for supercritical fluid measurements. This cell system has an NMR cell in which convection is prevented. A reactive gas and a reactive liquid can be smoothly introduced into the NMR cell. The oxygen (air) inside the NMR cell can be removed before measurement. The NMR cell system comprises a cylindrical cell, a cell holder, and an external pumping system. The cylindrical cell and the cell holder are made of a nonmagnetic material that withstands high temperatures, high pressures, and strong acidity. A pipe is mounted inside the cell holder to connect the external pumping system into the cell. A high-pressure cell for use with an NMR spectrometer is also disclosed. This high-pressure cell comprises a pressure-proof cell for receiving a sample, a pressure transfer tube for transmitting pressure to the sample in the cell, and a coupling portion for coupling together the pressure-proof cell and the tube.