To beef up natural immunity, we have used Bojoongikgitang which has been known to treat enervation in the oriental medicine. This study is analyzed out structure material and the chief virtue of a prescription through Literature Study on Bojoongikgitang and Clinical Application. And this study is investigated to make sure of the necessity and additional symptoms in using Bojoongikgitang. The results are as follows : 1. It is regarded that the structure materials of Bojoongikgitang consist of Astragali Radix one jeon(錢) five poon(分), Ginseng Radix, Atractylodis Macrocephalae Rhizoma, Glycyrrhizae Radix one jeon for each, Citri Pericarpium, Angelicae Gigantis Radix five poon for each, Cimicifugae Rhizoma, Bupleuri Radix three poon for each. 2. The necessity symptoms in using Bojoongikgitang are a pale complexion, drowsy eyes(目無精光), vigorless, lethargy, sluggish talk. 3. The fittest prescriptions prior to the necessity symptoms in using Bojoongikgitang are Bojoongikgitang added Paeoniae Radix Alba, Scutellariae Radix in fever, exterior heat, mild fever, Bojoongikgitang added Ephedrae Radix, Tritici Fructus Levis, Aconiti Iateralis Preparata Radix in spontaneous sweating, spontaneous sweating by yang deficiency, Bojoongikgitang added Paeoniae Radix Alba, Scutellariae Radix in feeling the pulse like a flood, largeness and weakness, scatter and largeness, flood and largeness for diagnosis respectively. Bojoongikgitang Entering the heart channel by culturing the blood prescription in vexation, vexation and anxiety, Soongihwajoongtang in headache, DossiBojoongikgitang in rigor, Bojoongikgitang annexed Saengmaecsan in thirst, Daninsamtang or Jojoongikgitang in asthma, asthma by congestion of the upwardness, Eeegongsan in light eating, eschewing food, losing one's appetite, Ikweeseungyangtang in deficiency failing to control blood and blood collapsey. 4. To treat a functional disease is superior to organic one in using Bojoongikgitang.