The high geochemical reactivity of boron and the large relative mass difference between ¹⁰B and ¹¹B lead to significant boron isotope fractionation in nature. So far the measured range of boron isotope composition (δ¹¹B) varies between –70 and +75‰. The negative δ¹¹B values are found in non-marine evaporite borate minerals and tourmalines, whereas positive δ¹¹B values are common in salt lake brines and evaporated seawater. Since the 1980s, with improved measurement methods, applications of boron isotope analysis have increased rapidly. At present, boron isotopes are successfully applied to reconstruct ancient marine environments, to determine depositional environments and ore genesis, to trace groundwater pollution and seawater intrusion, and to study continental erosion. This paper summarises the methods for boron isotope analysis, the mechanisms of boron isotope fractionation and the distribution of boron isotopes in nature, reviews the achievements and the problems of boron isotopes in geochemical applications, and proposes research directions of boron isotopes in geochemical fields.