In children, the poor intelligence and failing of study from it raise problems in mentality, character and society. The poor intelligence and failing of study are closely connected with brain, Xin(心), Shen(神), Jing(精), Qi(氣). In this paper, studying causes of the poor intelligence and failing of study, through documents, I can obstain such conclusions. 1. Xin(心) takes charge of brain and manages life, mind and mentality. 2. Shen(神) controls mind and Jing(精) is the origin of life. So Shen and Jing must be built up for increase of memory and study. 3. For increase of intelligence and study, Qi(氣) must go round smoothly. 4. Causes of the poor intelligence and failing of study are the lack of blood, damage of Shen(腎), huo(火), phlegm etc.