Theanine is an important component affecting tea quality and it has many health benefits for human being.Chemical synthesis of theanine had high productivity,but its application needed efficient raceme resolution technique.Although only L-theanine will be synthesized through exogenous/endogenous enzymes or microbe fermentation,low yield is the main shortage of this technique.Extraction of theanine from tea leaves is a conventional and efficient preparation technique,and highly purified theanine can be achieved when extraction and separation procedures are suitable. Theanine is an important component affecting tea quality and it has many health benefits for human being. Chemical synthesis of theanine had high productivity, but its application needed efficient raceme resolution technique. Although only L-theanine will be synthesized through exogenous / endogenous enzymes or microbe fermentation, low yield is the main shortage of this technique. Extraction of theanine from tea leaves is a conventional and efficient preparation technique, and highly purified theanine can be achieved when extraction and separation procedures are suitable.