Abstract: The present disclosure provides a tea plant CsFAAH6 gene and use thereof. The tea plant CsFAAH6 gene has a nucleotide sequence shown in SEQ ID NO: 1 in sequence listing. A protein coded by the tea plant CsFAAH6 gene has an amino acid sequence shown in SEQ ID NO: 2 in the sequence listing. The CsFAAH6 is highly expressed in mature leaves of tea plants; there is significant negative correlation between theanine content in shoots (one bud and two leaves) of different tea cultivars in different months and expression level of the CsFAAH6; instantaneous silencing of CsFAAH6 expression can significantly increase the theanine content, indicating that CsFAAH6 has a physiological function of theanine degradation and a molecular mechanism thereof.