Abstract: Three Methods for Calculating Molecular FormulaYu Zhili(Institute of Medicinal Biotechnology,Chinese Academy of Medical Sciences and Peking Union Medical College,Beijing 100050,China)Received Abstract:In this papre three methods for calculating molecular formula of compounds are described by mass spectromery(MS),element analysis and 13C-nuccear megnetic resonance(NMR).Keywords:molecular formula,mass spectrometry,~(13)C-NMR,element analysis