Sichuan brick tea (Kang Zhuan) contains different tea polyphenols from green tea and black tea. The inhibition on Fatty acid synthase (E.C.2.1.3.85, FAS) by the extracts of brick tea is measured by inhibition kinetics. FAS has been reported as a potential new therapeutic target for both cancer and obesity. The results show that the inhibition included both reversible and irreversible process. The optimal solvent for extracting FAS inhibitors is 50% ethanol. The extraction achieved during 5 hours in room temperature. The boiling water could extract about total 60% effective FAS inhibitors by two times extraction. The final efficiency is two-folds of that for green tea, but longer time is needed for the extraction. The inhibition of FAS by new brick tea was not stronger, and brick tea stored for several years showed most inhibitory activity. More storage time lead to decrease some inhibitory ability of brick tea but not very much for over 20 years. It is seems that the storage over 30 years markedly weakens the ability of brick tea. The brick tea extracts inhibited the overall reaction of FAS in a mixed manner of competitive and noncompetetive with acetyl-CoA and malonyl-CoA. It inhibited the ketoacyl reduction of FAS weakly, which indicated that the ketoacyl reductase domain is not the main reacted site that brick tea extracts attracted. These results shows that inhibitor in brick tea is different from that in green tea and black tea. It is proposed that the effective in brick tea should be theabrownine(TB), which inhibitory ability is higher than catechins and is closed with theaflavins. The results exhibited applicable foreground of brick tea for fat-reducing and anti-cancer.