Abstract: Cadmium is a typical chalcophile element which occurs in various sulfide deposits. In the environmental system, cadmium as the nutritional requirement is utilized for the growth of microorganisms, and its cycle is greatly affected by the biological process. Several recent publications have shown that mass differences between Cd isotopes result in isotopic fractionation during the evaporation/condensation processes, biological and inorganic processes. These results demonstrate that Cd isotopes can be used as a tracer in geosciences and environmental sciences. The Multiple Collector-Inductively Coupled Plasma-Mass Spectrometry (MC-ICP-MS) has successfully been used for high-precision measurements of cadmium isotopic compositions in the geological samples, which makes a rapid advance in the geochemical research of the cadmium isotope. In this paper, based on current publications, a review of the cadmium isotopic system is provided in detail, with emphasis on the geochemical behaviour of cadmium and its isotope fractionation mechanism, the distribution characteristics in the natural reservoirs, analytical technique and the applications in the geosciences and environmental sciences. The geochemical research of the cadmium isotope is just in its infancy; conducting an investigation into the cadmium isotope fractionation mechanism, the distribution characteristics in natural reservoirs and a unified cadmium isotope standard calibration system could promote the application of the cadmium isotope in geosciences and environmental sciences.