Rare gas isotopes, especially helium and argon isotopes, are sensitive to trace the origin of the ancient ore-forming fluids. Rare gases in different spheres of the earth have different characteristic isotopic ratios. The rare gas isotopic ratio in the fluid inclusions of the samples is determined, and
 the influence caused by all kinds of latter processes from the measured data is ruled out. Comparing the above result with the characteristic values in different reservoirs in Earth, we can trace the origin of ore-forming fluids and further discuss the mineralization mechanism for some deposits. The progresses of tracing ore-forming fluids in different kinds of ore deposits using rare gas isotopes are summarized, and some problems and the developing tendency about this method are also discussed.