本文主要探討的是許衡的理學思想，以及他繼承與發展程朱之學的特點。許衡早年受到王弼思想的影響，爾後轉向程朱之學。在理氣論上，他重視「自然」的概念，並將探討重心放在「氣中之理」；在心性論上，許衡強調心之「氣服於理」，則人的良知良能，自然能隨感而見，但是若氣不服於理，則人心會流於惡，無法發揮道德判斷的作用。因此，若要讓人去惡從善，則需要藉由主敬、行禮和格物致知等工夫，變化氣質。許衡在為學上重視踐履篤行的態度，對明代朱子學的發展，影響甚深。

This article aims to investigate the Neo-Confucianism (lixue 理學) theory of Xu Heng許衡, and his features of the development and succession from the Cheng–Zhu learning 程朱之學。 Originally, Xu Heng許衡got influenced by the theory of Wang Bi王弼in his early age, then got transferred to the Cheng–Zhu learning 程朱之學 later. Based on his theory of “li-qi” 理氣論, he emphasized on the concept of “Nature”自然, focusing on the investigation of li理in the qi氣. Also, in his theory of Mind-Nature心性論, he emphasized that if the qi is obedient to li, appearing on the mind, human being’s innate knowledge and ability instinct(良知良能) can occurs after a sensation.If the qi氣 is not obedient to li理, the human mind will tend to the evil, losing the function of moral judgment. Thus, if people would like to exterminate the evil and follow the good, it is needed to transform the physical nature by the work of keeping reverence主敬, practicing the rituals行禮, and“investigating things and extending knowledge to the utmost”(gewu zhizhi格物致知). Therefore, Xu Heng許 whose attitude of emphasizing the sincerely working, brought the deep influence on the development of Zu Xi's theory in the Ming dynasty.