Objectives : Shanghanlon is based on the Hwangjenaegyeong(黃帝內經)'s theory. Therefore, the contents of the Naegyeong can interpret Shanghanlon's provision, Chengwuji(成無己) followed the same way. Therefore, I studied the relationship between the symptom of Shanghanlon and the defensive Gi(衛氣), I try to prove that the Naegyeong is the theoretical basis of Shanghanlon. Methods : Naegyeong explains that defensive Gi protects the outer parts of the body, and runs the outer parts of the body. So I will explain the spontaneous sweating(自汗) aversion to cold(惡寒) pain(痛症) fever(發熱) difficulty of urination(小便不利) using the function of defensive Gi. Results & Conclusions : The defensive Gi and the nutrient Gi(營氣) run together, if the defensive Gi is weak, can not protect the nutrient Gi. If the defensive Gi does not perform the function of inducing astringency(固攝), the symptom of spontaneous sweating appears. If aversion to cold is caused by the weak of defensive Gi, we use the treatment of warming the Yang(溫陽). If aversion to cold is caused by the defensive Gi can not run, we use the treatment of activating the Yang(通陽). If the Gi and Blood(氣血) is not feeding properly, the pain occurs. In this case, we use the treatment of activating the Yang(通陽). The fever is caused by the stagnation of defensive Gi. If the defensive Gi is weak, the symptom of difficulty of urination appears.