The liquid level measurement for high-temperature and high-pressure vessels in nuclear power plants (such as pressurizers and steam generators) all adopts the pressure principle. Affected by the state of the medium inside the vessels and the operating conditions of the system, differential pressure liquid level measurement suffers from issues of low accuracy and poor reliability. Radar level meters, featuring high precision and reliability, represent an effective means for liquid level measurement in high-temperature and high-pressure vessels. In view of this, a split-type guided-wave radar with FMCW (Frequency Modulated Continuous Wave) modulation based on the Frequency Domain Reflectometry (FDR) principle is proposed for liquid level measurement. This technology can effectively eliminate the influence of obstacles such as heating elements, reference tube water supply devices, and reference tube nozzles inside the vessels, achieving blind-zone-free liquid level measurement and meeting the liquid level measurement requirements for high-temperature and high-pressure vessels in nuclear power plants.