With the progress of medical technology and the declining birth and death rates year by year, the population structure of Taiwan presents the aging phenomenon, which increases the demand for long-term care. The elderly often have many chronic diseases, mainly the so-called “Three-High Diseases”, which refer to hypertension, hyperglycemia and hyperlipidemia, and are related closely to our daily routes, healthy diet, and psychology. In order to establish a home care system for the elderly, this research takes the Four-Whole-Care System as one of the main concepts. The Four-Whole-Care System includes four items, whole person, whole process, whole family, and whole team, which provides continuous, comprehensive, and adaptable long-term care service. However, the Four-Whole-Care System has numerous fuzzy and uncertain items, which require a clear standard scope be defined through the inference of the Fuzzy Theory, as a warning standard to warn and remind the elderly and their family members. This research establishes a home care system for the elderly suffering from the Three-High Diseases, and sets up App service software to send out warnings of the Three-High Diseases in combination with the Four-Whole-Care System. We apply fuzzy theory to define and express a clear warning standard scope and assist the elderly and their family members to receive warnings of the Three-High Diseases. Our system also provides appropriate improvement suggestions, in order to enhance the quality of life of the elderly and provide care service more efficiently.