Abstract: Magnetic resonance spectroscopy based on the principles of magnetic resonance, the chemi-cal shift, and spin coupling is a technique that allows examination of the metabolites and biochemical nature in vivo without the need for invasive procedures. Non-invasive detection of metabolite concentration using MR spectroscopy can provide valuable information in diagnosis and treatment of diseases. In localized brain MR spectroscopy, the measurement results of brain metabolites had often been expressed as ratios rather than as absolute concentration; however, drawbacks of ratios have been mentioned in the literature. More recently MR spectroscopists have paid attention to acquire absolute concentrations using internal reference or external reference filled with brain metabolites. Concerning metabolite analysis in clinical MR spectroscopy studies, absolute concentrations have advantages over metabolite ratios. This article reviewed the principle of MRS and its methods in quantitative measurement of brain metabolite concentrations.