There is a common saying in academia that “mind” is the most common, basic and general category in the category system of ancient Chinese philosophy. Mind is an important part of Mencius’ thoughts. Mencius constructed a relatively complete the theory of mind and was the first to combine mind with nature and presented the goodness of human nature. As Gorlée (1994) put it that without any human mind or non-human mind, there is no sign interpretation, and also there is no sign action, so there is no sign activity. In China, there are fewer study on Mencius’ doctrine of mind from semiotic perspectives. Thus, this article aims to study the sign relation of the Chinese character 心 (xin, mind) into other signs so as to know about how it is used in the work Mencius, and to explore the meaning of the mind ( 心 , xin) within Mencius’ philosophical thought as well as to identify the sign transformation of mind-word-action so as to know about moral value of Mencius’ theory and to discover the semioethic thoughts in Mencius’ doctrine of mind. The statistic for the number of the Chinese character 心 (xin, mind) is 125 in the book Mencius. According to the sign relation of the Chinese character 心 (xin, mind) into other signs, they will be classified into six categories. Mind, word and action can transform into and educate each other reciprocally. Mind functions as the mediation between the transformation of word and action in the dynamic sign activity since word and action cannot directly be transformed into each other. Mencius’ doctrine of mind presents that we all subject to the responsibility and subject of the responsibility for life and for the other which demonstrates Chinese semioethic thoughts in politics, economics and education.