The invention relates to the field of medical technology. Ethyl 6-bromocoumarin-3-carboxylyl L-
theanine, a novel synthetic compound, can inhibit the growth and invasion of 
cancer cells of 
human lung cancer, 
breast cancer, 
liver cancer, gastric 
cancer, colon cancer, prostatic cancer, 
pancreatic cancer, 
cervical cancer, lymphadenoma, 
leucocythemia, 
melanoma, and the like, and can remarkably inhibit the growth and 
metastasis of the tumors in a body, with an inhibiting effect exceeding the inhibiting effects of anti-
cancer drugs. The 
mechanism of action involves the down regulation inhibition of the bonding of the receptors which are closely related to growth, invasion and 
metastasis of the tumors, 
signal transduction regulation and control proteins, the 
kinase level and a nuclear factor with 
DNA, and also upper regulation of factors such as cancer-inhibiting proteins and 
cell cycle inhibition proteins. The ethyl 6-bromocoumarin-3-carboxylyl L-
theanine can directly inhibit the activity of 
histone deacetylase, the activity of histonemethylferase EZH2, and combination of a inflammatory factor NF-[Kabba]B and 
DNA. The activity of the ethyl 6-bromocoumarin-3-carboxylyl L-
theanine exceeds the activity of the anti-
cancer drugs. The invention provides new applications of the ethyl 6-bromocoumarin-3-carboxylyl L-theanine for prevention and treatment of diseases such as tumors, 
inflammation, heart and cerebral vessels and 
immunodeficiency.