In recent years, multiple_collector inductively coupled plasma mass spectrometry (MC-ICP-MS) has been increasingly used for precise and accurate measurement of transitional metal isotopes, which has greatly improved precision, accuracy, and efficiency of molybdenum isotope analysis of geological samples, andalso made Mo isotopic geochemistry a new frontier in Earth science. This paper presents a review of the recent progress in the systematics of Mo stable isotopeand its application in geology. The natural range of δ98/95Mo is from－1.35‰ to 2.6‰. The fractionation of Mo isotopes in an oxidizing environment is mainly attributed to the adsorption of dissolved Mo on Mn-oxides, whereas that in an suboxic-euxinic environment is controlled by the content of H2S dissolved in water. Mo isotopic signatures in sediments can be used as an indicator for redox conditions of paleo-environment and corresponding paleo-oceanography. Therefore, molybdenum isotopes can be used as a powerful tool for understanding the redox conditions of local or regional depositional environment, the biogeochemical cycle of sulfur or carbon, and the geochemical evolution of ancient oceans. It is believed that, with further studies of the molybdenum isotope fractionation mechanism, molybdenum isotopes will certainly be applied to more and more areas in earth and environment sciences.