Abstract: Since secondary school is an important period for students' physical and mental development, the left-behind experience of students will leave a deep imprint in their growth. Certain inadaptation among freshmen of having left-behind experience appeared after entering college, which reflects the serious defects of students' mental health education in secondary school. Paying close attention to their sound personality and moral development requires the joint efforts of school, family and society. In order to reduce and prevent the left-behind students who are unable to adjust to college life, mental health education needs to be strengthened in the elementary education, especially secondary school.