Abstract: The recent advances in the research methods and mechanism of nicotine forms and distribution in tobacco and tobacco smoke at home and abroad were reviewed in two aspects:1) extracting and determining the free nicotine in tobacco or tobacco smoke with solvent, and then revealing the relationship between the content of free nicotine and tobacco pH (or tobacco smoke pH);2) obtaining the distribution profile of nicotine in tobacco and tobacco smoke directly from ¹H NMR detection.The theoretical calculations relevant to the forms of nicotine and some other tobacco alkaloids, ¹H NMR method and the concept of "effective pH" were introduced.The possibility and means for developing the relationship between "effective pH" and tobacco pH or tobacco smoke pH were also discussed.