Boron has two stable isotopes (¹¹B and ¹⁰B), chlorine also has two stable isotopes (³⁷Cl and ³⁵Cl). The large different in mass ( 11 and 10, 35 and 37) make both boron and chlorine exist big isotopic fractionation in the nature. Variations of boron and chlorine isotopic compositions had not been found in early investigations due to poor precision of determing boron and chlorine. Since 1980s, with some high precise methods of determing boron and chlorine isotopes, the variations of boron and chlorine isotopes in nature have been evidenced by high precise determination and a lot of investigations. δ¹¹B range from -30‰ to 60‰, and δ³⁷Cl range from -2‰ to 7‰.
    Many significant work about boron and chlorine isotopic geochemistry have been maken in oceans, salt lakes, groundwater, evaporated sediment and hydrothermal fluids. This paper give a brief summary of including analytical methods and application in Earth sciences.