Very-long-wave infrared (VLWIR) detection plays an irreplaceable role in fields such as space remote sensing, deep space exploration, and infrared spectroscopy. HgCdTe is an ideal material for VLWIR detection due to its continuously tunable bandgap. However, managing the high dark current and ensuring material uniformity, both consequences of its extremely narrow bandgap, remain core challenges. This paper first reviews the research progress of VLWIR HgCdTe detectors and the evolution of international performance evaluation standards for HgCdTe detectors. Then, it analyzes the structural evolution and operating principle of mainstream devices. Finally, an outlook on the key technological challenges and future research directions for VLWIR HgCdTe detectors is presented.