Decision tree is a very popular method of data mining. This paper introduces the theory of decision tree to analyze the structure of the decision tree, C5.0 algorithm discussed the idea of their advantages and disadvantages. in-depth understanding of the main factors of psychological symptoms and mental health of college students, the C5.0 algorithm is applied mental Health assessment data mining results based on a better understanding of students' mental health problems, to carry out a mental health education colleges and universities have practical significance.