With the coming of aging population in the society, the population of dementia became more numerous. This change has raised the attention of the ethical issue of how to treat the dementia patients, and at the same time, preserve their dignity, and also how to improve their life quality. In this article, the issue of how to preserve the right and benefit for dementia patients in different stages of the disease was firstly discussed, which included the differentiation of critical interests and experiential interests; then it was followed by the discussion of the individual integrality and its effect on the best right and property of life on the basis of the integrality as an individual. In conclusion, for patients who suffered from dementia, even at the end stage, same emphasis should be put on to both their critical interests and experiential interest. To respect the critical interests of these patients before they suffered from the disease is to certify their dignity. From the ethical point of view, however, if it is the case that a patient is able to receive the love and care from some other people, and react to be a positive feedback, then to respect the patient's experiential interests can be regarded as to respect his/her dignity of life.