The present work reports the positive effect of green tea extract EGCG on the improvement of Alzheimer’s and obesity mice with the administration of 50 mg EGCG/kg mice every day for 30 days, and the mechanism is elucidated from three aspects of mice body, biochemical indexes and tissue immunology. The results showed that the EGCG can improve the cognitive function of Alzheimer’s mice, its function mechanism is probably attributed to enzyme activities of choline acetyltransferase (AchE) and acetylcholine esterase (ChAT), as well as the content of malondialdehyde (MDA) in serum and the accumulate of β-amyloid protein 42 (Aβ42) in the hippocampus. Furthermore, EGCG has a positive effect on the inhibition against obesity desease, it is related to the enzyme activities of lipase and amlyase in serum of obesity mice, which will affect triglycerol metabolism and energy intake. It is worthily noticed that EGCG can protect obesity-induced liver tissue damage. The findings in this work will provide future directions for development of green tea functional foods.