The purpose of this article is to oversee the theory of Chimibyeong(治未病). The aim of Chimibyeong theory is to prevent disease from occuring, worsening, being delivered and so on. In many books, the word Chimibyeong was used as an alternative name for Yangsaeng(養生) or used as a term of preventing a disease or used as a word meaning treating disease in the early stage. But after the period of "Nangyeong(難經)", people extend the meaning of Chimibyeong to all stages of a disease covering the healthy stage, the early stage, the progressive, and the recovery stage of a disease. Especially in urgent cases when pathogenic factor[邪氣] attacks patient to critical situations, it is also regarded as one way of Chimibyeong to repel pathogenic factor out as soon as possible with proper medicines. These days people suffer from increasing mental stress, lack of rest and human relationships, environmental pollution and chronic diseases and so on, and the situation will grow worse. Many governments employ the health policy where preventing disease takes the highest priority because by doing that they can save a huge budget and minimize the economic and social disorder. In this circumstances the idea of pursuing prevention in the theory of Chimibyeong will help people to maintain healthy conditions.