The up-stream molecular causes of Alzheimer's disease (AD) have been discussed from the aspect of carbonyl stress, which represents an important common biochemical process of human aging. Firstly, chemical reactions of carbonyl toxification, induced by free radical oxidative stress and glycation stress, on lipids, carbonhydrates and proteins are elaborated. Secondly, evidences of reactive carbonyls and their effects on cellular structure and functions in AD patients are provided. Finally, detoxification mechanisms against carbonyl stress in brain are analysed and summarized, and strategies based on the mechanism for treating AD, as well as for preventing aging, fatigue and sub-health are also introduced and discussed.